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  #1  
Old 04-23-2009, 09:56 AM
tdn tdn is offline
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Swimming: Do some people sink like a rock?

The swimming thread in IMHO got me to thinking about this.

Some people who can't swim say that they sink like a rock. Is this possible? Aren't we all built more or less the same? Or is there some magic body fat percentage that makes one wholly unboyant?

I sometims suspect that some people feel themselves start to sink a little (which is normal), then panic and give up forever. But I could be totally wrong about that.
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  #2  
Old 04-23-2009, 09:58 AM
Philster Philster is offline
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Body fat helps buoyancy, because more water is retained in the body.

Higher body fat % = more buoyancy; hence the body-fat calculation method that sees people dipped into large tanks of water to determine their body fat %.

helpful...

"Why don't we float alike" article:

http://www.google.com/url?sa=t&sourc...xzqEksZul-3TNw


http://en.wikipedia.org/wiki/Body_composition

Last edited by Philster; 04-23-2009 at 10:00 AM..
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  #3  
Old 04-23-2009, 10:05 AM
billfish678 billfish678 is offline
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I can tell you I DONT float well. Fully inhaled and held breath, totally motionless, in fresh water I am lucky if I dont sink. Salt water, just the very top of my head is above water.

I have to tread water to actually breath. I also can't sorta float on my back like some. My lower half is defininetly not bouyant and without fighting it, my body assumes a vertical, not horizontal position.
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Old 04-23-2009, 10:10 AM
tdn tdn is offline
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Originally Posted by billfish678 View Post
I also can't sorta float on my back like some. My lower half is defininetly not bouyant and without fighting it, my body assumes a vertical, not horizontal position.
Do you put your head back? The thing is, if you lift your head, your lower body will sink. And if you're a little panicky about sinking, your natural reaction would be to raise your head.

One thing I've found is that floating is largely an act of faith.
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Old 04-23-2009, 10:17 AM
mazinger_z mazinger_z is offline
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If I try to lay back, I can float on my back, but my legs dip. But, I can breathe, and possibly survive out in open water (or so my logic tells me).

If I try to tread water, no amount of flailing will cause me to float, and I'll probably exhaust myself in a minute. At best, the water is at mouth level. If I do nothing and try to remain buoyant (like sitting back in a seat), the water level is at least 4 inches above me.

I can also sit at the bottom of a diving well, no problem, as well as lay down there in a prone position and act as if I were dead.
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Old 04-23-2009, 10:32 AM
Chefguy Chefguy is online now
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I recall that in bootcamp, when we had to step off the one meter platform whether we could swim or not, one fella did indeed sink to the bottom. While most people will at least float to the top, this guy just sat on the bottom, waiting to be rescued. Weirdest thing I ever saw.
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  #7  
Old 04-23-2009, 10:40 AM
Henrichek Henrichek is offline
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Witches!

Personally I have never managed this act of witchcraft myself. With a lungful of air and relaxing I normally end up on the bottom of the pool. Maybe it'd work in salt water.
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  #8  
Old 04-23-2009, 10:40 AM
billfish678 billfish678 is offline
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Originally Posted by tdn View Post
Do you put your head back? The thing is, if you lift your head, your lower body will sink. And if you're a little panicky about sinking, your natural reaction would be to raise your head.

One thing I've found is that floating is largely an act of faith.

I am not all panicky about water or sinking. I used to love exhaling and sitting of the bottom of the pool because I could do it so well. If I exhale, I definitley sink like a stone.

Under extremely favorable (laboratory) conditions, I might be able to keep a nostril barely above water without treading. If I am inhaling and exhaling (unless I exhale REAL fast, then inhale and hold it) my average bouyance is darn close to zero, if not negative.

I used to practice all that stuff they tell you to do survive long periods in/on the water. None of the low energy stuff even came close to working for me.

Open water? I gotta tread some to breath.

Thats why no mater how warm the water is, I always wear a wetsuit scuba diving. I want some guaranteed positive bouyance that will keep my head easily above water should something bad happen and I end up alone in the ocean for awhile.
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Old 04-23-2009, 10:45 AM
Balthisar Balthisar is offline
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Originally Posted by Philster View Post
Body fat helps buoyancy, because more water is retained in the body.
When I was getting my open water certification, I regularly had to use every leftover weight on the boat. I'm not a freaky monster fat-wise, but my height paired with my fat makes a lot of fat overall compared even to small, normal people that have a higher BFI. All the same, it's embarrassing using all of the leftover weights.

I mean to take up freshwater diving next, and have no plans to try the Great Salt Lake or the Dead Sea.
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  #10  
Old 04-23-2009, 10:54 AM
Really Not All That Bright Really Not All That Bright is offline
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Anyone will sink if they exhale. I float and I have almost no body fat at all.
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  #11  
Old 04-23-2009, 11:17 AM
Markxxx Markxxx is offline
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I can't swin and I sink like a rock. I am pretty sure it is because I'm so tense in the water. Dead people float (well mostly) but even if I am in the bathtub, I can relax my arm and have it float but as soon as I notice it, it sinks.

I think a fear of water or stress effects you without you noticing it. I know thin people who float and fat people that sink, at least in my case and the people I've known we've had some kind of water fears or issues.
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  #12  
Old 04-23-2009, 11:19 AM
billfish678 billfish678 is offline
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Oh, I forgot to add, the OP noted that people who "can"t swim" claim to sink like a rock.

I consider myself a decent swimmer, been doing it since I could walk. I canoe, I sail, I scuba, I've even cave dived a few times. I have no inate fear of water.

So, at least in my case, my poor floating abilities have nothing to do with some mental projections of a fear of water or lack of swimming skills.
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Old 04-23-2009, 11:32 AM
chowder chowder is offline
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At one time I could not swim a stroke. I got cheesed off just sitting by the pool when on hols so I took swimming lessons.

I was totally useless, flailing about, arms and legs all going in different directions and eventually I sank like a stone.

Now after umpteen lessons I can swim, not a lot and not very well, but at least I can now join in the frolics in the pool and get to ogle the ladies up close
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Old 04-23-2009, 11:40 AM
KneadToKnow KneadToKnow is offline
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I can swim if my life depends on it, but it looks like I'm swimming as if my life depends on it.

Repeated efforts at floating have done nothing. I'm in billfish678's situation. I go vertical and slide into the water like the Titanic.
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  #15  
Old 04-23-2009, 11:45 AM
tdn tdn is offline
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Originally Posted by billfish678 View Post
Oh, I forgot to add, the OP noted that people who "can"t swim" claim to sink like a rock.
Please ignore my broad brush.
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  #16  
Old 04-23-2009, 11:48 AM
astorian astorian is offline
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I wouldn't have believed it if I hadn't seen it decades ago, but former heavyweight champ Joe Frazier sank like a stone in the pool during the swim race in an episode of "The Superstars." Many observers really thought he was going to drown. Eventually, he managed a weak dog paddle and completed the race about 20 minutes after everyone else.

He admitted later he didn't know how to swim, but thought he'd give the swimming race a try anyway.
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Old 04-23-2009, 11:57 AM
minor7flat5 minor7flat5 is offline
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Totally dependent on body fat.

I'm borderline.

When I am in my swimming pool, if I exhale, I will slowly drop to the bottom. I can then sit happily there, freaking folks out, until I feel the desire to breathe.

If I have a lungful of air, my head stays above the surface.

I imagine some totally ripped dude would drop like a stone due to a low BMI.
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  #18  
Old 04-23-2009, 12:24 PM
SlowMindThinking SlowMindThinking is offline
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Being able to swim has little to do with body fat: look at Olympic swimmers, or even your garden variety triathlete.

Being able to float correlates to body fat, but also muscle tissue. I took a lifesaving class as a student at a large, state school. One guy in the class wrestled. He was in great shape and had as little body fat as anyone. Another student was a girl in good enough shape to swim and pass the class, but more overweight than anyone else in the class. The instructor actually used the two of them as demos. The wrestler maintained perfect floating form to the bottom of the diving pool, while the girl didn't seem to break the water's surface tension.
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  #19  
Old 04-23-2009, 12:32 PM
crazyjoe crazyjoe is offline
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My dad served in the navy, and swims well. He can take a full breath and sink to the bottom of the deep end of the pool (10 - 11 feet). At least, he used to be able to...he is 70 and hasn't been in a pool in a while. He's 5'3" and weighed in at 160 - 170lbs. He was strong, but nothing about him said "bodybuilder" and he had quite the gut. The gut did not float.
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Old 04-23-2009, 12:33 PM
Projammer Projammer is offline
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The last time I was in water I was borderline. I'd float so long as I had a reasonable amount of air in me. If I exhaled and didn't breathe in again before I went under I'd soon be at the bottom.

I've put on a little padding so I might be a bit better off now.
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  #21  
Old 04-23-2009, 12:36 PM
bouv bouv is offline
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Originally Posted by mazinger_z View Post
If I try to lay back, I can float on my back, but my legs dip. But, I can breathe, and possibly survive out in open water (or so my logic tells me).
Maybe this is where part of the problem lies. This is normal. I float very well, and have almost no body fat (and had even less in high school when I swam and floated even better.) When you lie back, your legs will start to sink. The key is to let them and not try to fight it. Keep a lungful of air, and your chest and head will stay afloat. Your posture when floating is essential.

I also see everyone mentioning floating on their back. Crazy as it sounds, have you tried floating on your stomach? You float better face-down. I remember my swim instructors in elementary and high school telling us that if the water was calm, and we thought it might be a long while before we get help, that face down will save more energy while floating. You obviously have to lift your head up every so often to breath, and if you don't have a good lung capacity it might not be good, but I find it relaxing and easier than floating on my back.


And I'm fully capable of sitting on the bottom of the pool as well. A full set of lungs or an empty set of lungs works wonders for buoyancy.
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  #22  
Old 04-23-2009, 01:19 PM
constanze constanze is offline
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A friend who taught very good swimming courses (for kids and adults) had a test he did with the adults* early on (after getting them used to water-in-the-face, one of the earliest lessons). He took them into the corner of the deep pool, where the bottom was over 3.50 meters down (ca. 3.5 yards), and each person went slowly into the water, holding onto the edges, then took a deep breath and pushed downwards, until the head was under water, and the air in their lungs + the fat buoyed them up again. It was quite impressive to see the relief as they realized they would pop back up like a cork.
Important notice: the position of your arms - to the side or over your head - plays an important part in this.

Although I can swim well, I, too, was surprised by this, because I'd only ever tried vertical (Dead man's float), where you have stay rigid, otherwise skinny legs will sink.

* He said that the body-fat rate for children is not good enough for this test.

Generally, I think that people who act all phobic about not being able to swim, or being able to learn, should get a grip and a good, sensitive teacher with a well-developed training plan. (No, my friend doesn't want to do it anymore, he's fed up. And he's in Munich.)
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  #23  
Old 04-23-2009, 01:53 PM
tdn tdn is offline
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I posted my OP a wee bit late, as I was doing a lot of thinking about this last summer. I tried a neat little experiment, and I'd encourage chronic sinkers to try it too. I'd be interested in the results.

Go to the deep end, or at least to where you can barely touch bottom. Hold on to the side of the pool loosely. Relax your body and let it do what it wants. When it has settled to wherever it wants to be, take a breath and stick your face in the water. Again, let your body do what it wants. Don't force anything. After a minute, take your face out of the water. Then back in.

I can play sinky-floaty all day long!
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  #24  
Old 04-23-2009, 03:18 PM
oboelady oboelady is offline
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Originally Posted by tdn View Post
I posted my OP a wee bit late, as I was doing a lot of thinking about this last summer. I tried a neat little experiment, and I'd encourage chronic sinkers to try it too. I'd be interested in the results.

Go to the deep end, or at least to where you can barely touch bottom. Hold on to the side of the pool loosely. Relax your body and let it do what it wants. When it has settled to wherever it wants to be, take a breath and stick your face in the water. Again, let your body do what it wants. Don't force anything. After a minute, take your face out of the water. Then back in.

I can play sinky-floaty all day long!
Former lifeguard and swim team member - I sink like a rock if I try to float motionless on my back. Everyone, however, will float near the surface if you hold your breath and lean forward. I don't know if they still teach this, but, the sinky-floaty routine is the best way to not drown and conserve energy if you are going to be stuck in the water for a long time. It takes a lot of energy to keep your head out of the water full time. If, instead, you put your face in the water, let your arms float next to your head, and, as much as is possible, try to "lean forward" so you don't go completely vertical, you will, depending on your body fat, either float on the surface, or float very close to the surface. When you need to breathe, exhale, then simultaneously lift yourhead, push down gently with your arms, and give one gentle scissors kick. This will raise your head out of the water. Take a breath and lower your face back into the water. Repeat as often as necessary. The key is to not kick and push so hard that you raise your head too far out of the water or else you will start to sink as you come back down. If you do start to sink, don't panic. You will slowly rise back up to the surface, or near the surface depending if you are a natural floater or not.
Even for a bunch of experienced swimmers, this took a little practice. The key is to minimize the upward movement to get your breath. The higher you raise your head, the further you sink afterward. Slow, gentle movements and you can sustain this for hours and hours. You can't tread water and keep your head out of the water for that long.
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  #25  
Old 04-23-2009, 03:24 PM
Stranger On A Train Stranger On A Train is offline
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Body fat does play a significant role in buoyancy. When I was doing DM certification, one of the exercises was to tread water for 15 minutes, and you got the highest mark for doing the last 3 minutes with hands out of the water. I could do this easily with just a light kicking motion and a moderate bit of bobbing; the slender Asian girl who was in the cert with me could barely tread water even using her hands. Technique (as described by oboelady) and comfort in the water also play a role, but some people simply don't float head up while others float naturally.

Stranger
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  #26  
Old 04-23-2009, 03:59 PM
Washoe Washoe is online now
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I don’t know if this is true, and I can’t remember where I read it (Fouts, I think), but supposedly the reason that chimpanzees can’t swim is that they have no body fat. Apparently, they literally do ‘sink like a rock.’

Family legend has it that I have an ancestor who was so obese that he could float on his back in the Caspian Sea and actually catnap while doing so.

Last edited by Washoe; 04-23-2009 at 03:59 PM..
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  #27  
Old 04-23-2009, 04:49 PM
Zyada Zyada is offline
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Human buoyancy is going to be a function of both body fat and body muscle.

Body fat density is ~ 0.9 g/cm-3 which is just slightly less dense than water (which is exactly 1 g/cm-3). Thus, if one were to put a chunk of fat (let's use steak fat) in water, the chunk would float.

Body muscle density, on the other hand, is slightly more dense than water at ~1.06 g/cm-3. A piece of lean meat from the same steer would therefore sink in the water.

cite: http://answers.google.com/answers/threadview?id=576481

The other types of tissue play into this as well, but it seems to me (haven't studied it) that these would not vary quite so much from person to person as muscle and body fat do. (Blood looks to be slightly more dense than water)

Since one's ability to float in water is a function of total density, then buoyancy becomes a function of what percentage of the body mass is muscle and what percentage is fat. If there is a great deal of muscle and little fat, the scales (so to speak) are going to tip over to the more dense than water side, and the person will sink. If the percentage of fat is higher, at some point the density will become less than water and the person will float. This also means that some people are close enough to a density of one that the a deep breath in can be the difference between sinking or floating.

Speaking of witchcraft... Healthy women in general have more body fat than healthy men with comparable body profiles. I believe that in general, healthy men are likely to sink, whereas healthy women are almost guaranteed to float. This means that the old test of throwing a tied up witch into the water would be less likely to show one of the menfolk as a witch
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  #28  
Old 04-24-2009, 08:03 AM
Damfino Damfino is offline
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When I was taught swimming as a kid, our coach made us take a deep breath and then grab our knees in a sort of foetal position. All of us were bobbing up and down like mushrooms with our backs above water. It was a great confidence-building measure and let us know that it needed no effort to float. We were pretty average physically, and age was about eght years. I don't know what sort of difference this might make.

Last edited by Damfino; 04-24-2009 at 08:05 AM.. Reason: Added information
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  #29  
Old 04-24-2009, 11:09 AM
constanze constanze is offline
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Originally Posted by Damfino View Post
We were pretty average physically, and age was about eght years. I don't know what sort of difference this might make.
I just talked again to my friend, and he confirmed: no human, no matter what the fat-muscle-bones to total body weight ratio is, will sink as long as air is in the lungs. Non-swimmers who do sink are probably so tense that they exhale. And if you are tense, it will feel more difficult to stay above water.

Technically, children before puberty (plus marathon runners, rock climbers and similar adult sportspeople with lots of muscle, low total weight, little fat) have the worst possible ratio of fat to total body weight, yet my friend has taught hundreds of the little buggers to float and swim. So yes, if 8-year old kids can float, any normal adult with air in his lungs can float.
And learning to swim is not directly related to floating anyway - an obese blob of 250 kg will float comfortably, but too limited in his motion range to swim effectivly.
The tenseness and lack of coordination for the new set of movements is what makes swimming difficult for beginners. Practice helps, not fat. And a good teacher who does confidence-building exercises like the one above.
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Old 04-24-2009, 12:18 PM
amarinth amarinth is offline
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Originally Posted by tdn View Post
Go to the deep end, or at least to where you can barely touch bottom. Hold on to the side of the pool loosely. Relax your body and let it do what it wants. When it has settled to wherever it wants to be, take a breath and stick your face in the water. Again, let your body do what it wants. Don't force anything. After a minute, take your face out of the water. Then back in.
I'm one of the sinkers. I also happen to love the water and love swimming. When I "relax and let my body do what it wants" it doesn't end up floating.

Luckily, I find this position comfortable and peaceful...meditative (like I said, I love the water). But it isn't floating the way I've seen other people float, or experienced it in a wetsuit. (The first time I wore a wetsuit, I was supposed to be practicing swimming in one. I didn't because the sensation of floating was so novel, I just played around with not sinking.) And if I were a more panicky type of person, less confident of my ability to swim, or didn't really like the feeling of being surrounded by water, I would be freaked out by other people's claims about what my body should do in the water when it obviously wasn't doing that. I'd say that such advise is incredibly unhelpful.
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Old 04-24-2009, 01:24 PM
Jurph Jurph is offline
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When I was at Air Force Field Training ("officer basic") in Texas, we spent most of July marching around, eating very small meals, doing extensive PT, and generally sweatin' to the oldies. Going into camp I had been a skinny mumblethumper, but by Training Day 20, when we got into Water Survival, I was probably down to 160 pounds with maybe 2 pounds of fat if I'd had bacon for breakfast.

We got into the pool and the Lieutenant showed me the dead man's float, which I had been doing in the Atlantic since I was four or five years old. I said "Yes sir, I know how it's done, but it's not working." The LT came over to give me some motivation and yelling, and finally asked to see what I was doing wrong. I splayed out and sunk right to the bottom of the pool. The LT laughed, asked to see it once more, and then said "You've got great form, but if your plane goes down over water you're a dead man. You get a pass. Now help your flight-mates with their form."

In retrospect, I was probably not filling my lungs very full of air; I was a long-distance runner and in the water I felt more comfortable with a half breath than a full chest-bursting inhalation.
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Old 04-24-2009, 01:32 PM
billfish678 billfish678 is offline
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. Going into camp I had been a skinny mumblethumper, but by Training Day 20, when we got into Water Survival, I was probably down to 160 pounds with maybe 2 pounds of fat if I'd had bacon for breakfast.
.
I am 5"8 or so and till recently if I was over a 120 lbs I was doing good.

How much fat and or muscle do you guys think I've had to counteract even denser bones? Plus my lung volume is rather on the small side.

I sink damint, or come darn close depending on whether its salt or fresh water.

I certainly don't float well enough to breath easily with my head above water.
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Old 04-24-2009, 06:01 PM
madrabbitwoman madrabbitwoman is offline
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I'm so floaty I have trouble duck diving. I can do a pin drop and end up with my head bobbing above the water. I suppose that if I were ever lost at sea there would be an advantage in not having to tread water.
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Old 04-25-2009, 08:23 AM
constanze constanze is offline
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We got into the pool and the Lieutenant showed me the dead man's float, which I had been doing in the Atlantic since I was four or five years old.
(Bolding mine)

I think that this is far more important than the increased muscle mass, unless you had been used to pool swimming before this test. In salt water like the Atlantic, because of the increased buoyancy, you move slower than in sweet water like a pool.

My friend said how when he spent several weeks in summer in Yugoslavia swimming in the Med., and then returned to Munich's sweet water pools, he felt as if the water had "holes" through which he kept sinking, until he had gotten used again to sweet water.
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Old 04-25-2009, 08:27 AM
constanze constanze is offline
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Originally Posted by amarinth View Post
I'm one of the sinkers. I also happen to love the water and love swimming. When I "relax and let my body do what it wants" it doesn't end up floating.

Luckily, I find this position comfortable and peaceful...meditative (like I said, I love the water). But it isn't floating the way I've seen other people float, or experienced it in a wetsuit. (The first time I wore a wetsuit, I was supposed to be practicing swimming in one. I didn't because the sensation of floating was so novel, I just played around with not sinking.) And if I were a more panicky type of person, less confident of my ability to swim, or didn't really like the feeling of being surrounded by water, I would be freaked out by other people's claims about what my body should do in the water when it obviously wasn't doing that. I'd say that such advise is incredibly unhelpful.
That's because it's difficult to give advise over the internet, instead of watching directly what you're doing. From the other description above, I suspect many people who are tense simply don't beath in well enough to fulfil the physics. Also, if you're tense and unsure, it's difficult to stretch out, which helps floating.

Or, you're a medical/physical oddity to every textbook. (Posting a video to youtube of how you're sinking won't help me, because I can't watch youtube on my system and with my connection.)
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  #36  
Old 04-25-2009, 12:00 PM
aruvqan aruvqan is offline
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Originally Posted by Washoe View Post
I donít know if this is true, and I canít remember where I read it (Fouts, I think), but supposedly the reason that chimpanzees canít swim is that they have no body fat. Apparently, they literally do Ďsink like a rock.í

Family legend has it that I have an ancestor who was so obese that he could float on his back in the Caspian Sea and actually catnap while doing so.
I would consider believing that. I am fat, and I float like a cork. I probably could catch a nap if the waves were calm.
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Old 09-11-2009, 10:49 AM
Qis Qis is offline
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Originally Posted by constanze View Post
I just talked again to my friend, and he confirmed: no human, no matter what the fat-muscle-bones to total body weight ratio is, will sink as long as air is in the lungs. Non-swimmers who do sink are probably so tense that they exhale. And if you are tense, it will feel more difficult to stay above water.

Technically, children before puberty (plus marathon runners, rock climbers and similar adult sportspeople with lots of muscle, low total weight, little fat) have the worst possible ratio of fat to total body weight, yet my friend has taught hundreds of the little buggers to float and swim. So yes, if 8-year old kids can float, any normal adult with air in his lungs can float.
And learning to swim is not directly related to floating anyway - an obese blob of 250 kg will float comfortably, but too limited in his motion range to swim effectivly.
The tenseness and lack of coordination for the new set of movements is what makes swimming difficult for beginners. Practice helps, not fat. And a good teacher who does confidence-building exercises like the one above.

Hey, Just thought i should chip in.
As a child i remember doing the exact same thing. and i remember floating.
Now i sink like a stone, big breath or none. if i take a lung-burstingly big breath in fresh water i still sink.

On the plus side, us sinkers can work on blowing bubble rings from the bottom of the pool with a our lungs full. floaters need to waste air to sink and so have less to blow rings with!!!

obviously I'm doomed if i pass out at sea.

I've been reading about free-diving, and I'm thinking that a sinker can't free-dive without armbands or a wetsuit

Any opinions?
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  #38  
Old 09-11-2009, 12:18 PM
BrotherCadfael BrotherCadfael is online now
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I'm another that sinks like a rock - I sink a bit slower than when I was twenty or so, as I'm not quite as lean as I was then.

It takes continual effort to stay afloat. I hear of people floating and treading water for hours on end, and it is simply incomprehensible to me, as I would be totally exhausted, to the point of drowning, in a relatively short time - not sure just how long, as i have never tried it..
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  #39  
Old 09-11-2009, 01:18 PM
The Great Sun Jester The Great Sun Jester is offline
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Originally Posted by crazyjoe View Post
My dad served in the navy, and swims well. He can take a full breath and sink to the bottom of the deep end of the pool (10 - 11 feet). At least, he used to be able to...he is 70 and hasn't been in a pool in a while. He's 5'3" and weighed in at 160 - 170lbs. He was strong, but nothing about him said "bodybuilder" and he had quite the gut. The gut did not float.
This is me except I'm not that old.

42, 195#, 5'5" stocky build. Charts say I'm 40-50 pounds overweight but I was Army fit back at 170#.

If I lay back straight, head and chest tipped back, full breath of air, My legs sink quickly and only my face from the ears forward is above the surface. I exhale, I sink like a rock.

Hairy beer gut notwithstanding, I can swim like a fish. Well, maybe a walrus.
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  #40  
Old 09-11-2009, 02:41 PM
corkboard corkboard is offline
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Originally Posted by constanze View Post
I just talked again to my friend, and he confirmed: no human, no matter what the fat-muscle-bones to total body weight ratio is, will sink as long as air is in the lungs. Non-swimmers who do sink are probably so tense that they exhale. And if you are tense, it will feel more difficult to stay above water.
I've been swimming comfortably since I was 5 (and boy, are my arms tired!). I'm not afraid of the water, I don't tense up, I have plenty of lung capacity (I'm a runner), and as far as I know, I'm human. But I can't float without at least some effort at treading water.

If I assume the spread-eagle positon, face up, my midsection/butt will sink first and pull the rest of me down after it, even while holding a deep breath. I won't go to the bottom, but will hang out subsurface. If I try to sort of 'pelvic thrust' my midsection up higher, my head and legs will cantilever down under the water.

For a long time I thought "floating" always involved at least some minimal water-treading efforts, until some friends and I got into the conversation while in the pool. I witnessed them actually floating on the water, while making no effort to stay like that. Try as I might, I just couldn't do it.

Your friend's expertise notwithstanding, I just don't think his comment applies to everyone.
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  #41  
Old 09-11-2009, 02:53 PM
BrotherCadfael BrotherCadfael is online now
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constanze, your friend frankly doesn't know what he is talking about. I've been there, alright? Fill lungs, hold breath, sink to bottom of pool. One factual counter-example to his blanket statement. Q.E.D.

Last edited by BrotherCadfael; 09-11-2009 at 02:53 PM..
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  #42  
Old 09-11-2009, 03:01 PM
The Great Sun Jester The Great Sun Jester is offline
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Originally Posted by BrotherCadfael View Post
constanze, your friend frankly doesn't know what he is talking about. I've been there, alright? Fill lungs, hold breath, sink to bottom of pool. One factual counter-example to his blanket statement. Q.E.D.
I wonder what would happen if you were in a container of water attached to an infinitely long, vertical treadmill that would move the tank of water down at the same rate at which you were sinking....
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  #43  
Old 09-11-2009, 03:06 PM
Henrichek Henrichek is offline
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Originally Posted by Inigo Montoya View Post
I wonder what would happen if you were in a container of water attached to an infinitely long, vertical treadmill that would move the tank of water down at the same rate at which you were sinking....
Unfortunately these people aren't around to come up with an answer to that question.
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  #44  
Old 09-11-2009, 03:29 PM
GargoyleWB GargoyleWB is offline
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Originally Posted by Damfino View Post
When I was taught swimming as a kid, our coach made us take a deep breath and then grab our knees in a sort of foetal position. All of us were bobbing up and down like mushrooms with our backs above water...
I tried this last time I was in a pool. I gradually sink and end up settling on the pool floor like a pasty white hockey puck 5'10", 165 lbs for reference. I suspect the position deflates the lungs considerably.

With the "lie back" position and a full deep breath, only my lips and nose remain above water, and the slightest water movement will slosh into my mouth. Exhaling means I sink.

Last edited by GargoyleWB; 09-11-2009 at 03:29 PM..
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  #45  
Old 09-11-2009, 03:36 PM
Mississippienne Mississippienne is offline
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Originally Posted by Chefguy View Post
I recall that in bootcamp, when we had to step off the one meter platform whether we could swim or not, one fella did indeed sink to the bottom. While most people will at least float to the top, this guy just sat on the bottom, waiting to be rescued. Weirdest thing I ever saw.
A recruit died this way during my ex-teammate's Marine boot camp. They think he purposefully sank hoping to get kicked out for not swimming. The instructors dived in after him, but he drowned before they tugged him back to the surface.
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  #46  
Old 09-11-2009, 04:19 PM
pulykamell pulykamell is online now
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Originally Posted by GargoyleWB View Post
I tried this last time I was in a pool. I gradually sink and end up settling on the pool floor like a pasty white hockey puck 5'10", 165 lbs for reference. I suspect the position deflates the lungs considerably.

With the "lie back" position and a full deep breath, only my lips and nose remain above water, and the slightest water movement will slosh into my mouth. Exhaling means I sink.
Same here. I've only been able to float successfully in the Mediterranean. Otherwise, no matter what I do, there's no way for me to keep my feet up. I've tried relaxed straight back position, heavily arched back position. Nothing. If I completely fill my lungs up with air and hold it, my face will be about 1/2 inch above the water line, but the instant I try to exhale and take another breath, I dip below. Basically, what happens is my legs start sinking and take the rest of my body with them. It doesn't matter how relaxed I am -- in a shallow, 4-foot pool, there's no reason for me to be tense about anything.
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  #47  
Old 09-11-2009, 04:52 PM
Apex Rogers Apex Rogers is offline
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I think lung capacity might play a bigger role than people are giving it. When instructed to take a deep breath, many people will raise their shoulders and suck in their stomach, not using their diaphragm to full capacity and will actually take a quite shallow breath. I'm wondering if these folks who sink are actually breathing properly, letting their chest and stomach expand to take in a full breath. A simple test might be to see how long you can hold your breath. If it's significantly less than a minute or minute and a half, that would indicate shallow breathing and hence less air to aid in buoyancy.

Last edited by Apex Rogers; 09-11-2009 at 04:54 PM..
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  #48  
Old 09-11-2009, 04:54 PM
pulykamell pulykamell is online now
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Originally Posted by Apex Rogers View Post
I think lung capacity might play a bigger role than people are giving it. When instructed to take a deep breath, many people will raise their shoulders and suck in their stomach, not using their diaphragm to full capacity and will actually take a quite shallow breath. I'm wondering if these folks who sink are actually breathing properly, letting their chest and stomach expand to take in a full breath. A simple test might be to see how long you can hold your breath. If it's significantly less than a minute or minute and a half, that would indicate shallow breathing and hence less air to aid in buoyancy.
I could hold my breath for just over two minutes.
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  #49  
Old 09-11-2009, 08:43 PM
Qis Qis is offline
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Originally Posted by Apex Rogers View Post
I think lung capacity might play a bigger role than people are giving it. When instructed to take a deep breath, many people will raise their shoulders and suck in their stomach, not using their diaphragm to full capacity and will actually take a quite shallow breath. I'm wondering if these folks who sink are actually breathing properly, letting their chest and stomach expand to take in a full breath. A simple test might be to see how long you can hold your breath. If it's significantly less than a minute or minute and a half, that would indicate shallow breathing and hence less air to aid in buoyancy.
Yeah, i just did 2:20 without any problems(well, besides losing the timer on the computer while i was doing it and having to frantically open the date/time while holding my breath). i reckon i could've gone longer. I'll need to try it in the pool next time i go for a swim...

Anyone on here know anything about free diving? Can us sinkers do it 'safely'? I'm guessing a wetsuit would make me buoyant... or armbands....
*rummages for some freediving forum...*
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  #50  
Old 09-12-2009, 04:36 PM
jackelope jackelope is offline
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Originally Posted by constanze View Post
I just talked again to my friend, and he confirmed: no human, no matter what the fat-muscle-bones to total body weight ratio is, will sink as long as air is in the lungs.
Sorry, but your friend is just wrong. I'm an excellent swimmer with not much body fat (BMI of 20.8, according to this site), and even if I take a big, full breath and relax my body completely, I sink. I don't sink "like a stone"; I sink slowly, feet-first. But I definitely sink.

I can keep myself at the surface with minimal effort if I do the "dead-man float" (full lungs, face-down), but I have to use my hands or legs just a little bit to do so. And obviously I can't stay that way for extended periods, because it involves keeping my air intakes underwater.
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