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…
Unfortunately these people aren’t around to come up with an answer to that question.
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.
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.
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.
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.
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…
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.
Didn’'t read all the replies but here’s what I know:
I’m a lousy swimmer, and have always had a bit of fear of water. Back in my youth I sported a sub-10% bodyfat (untrained sixpack showing), thin limbs, thin torso etc. I never sank like a rock no matter what I did. If people do that, low bodyfat / high density does not cause it.
I have read all the posts:
6’4’ from 170 lbs to 350 lbs and all place in between, 66 yrs old.
age 12 to 30, could actively swim under water for over 4 minutes. (barely)
Floating = inhale, at all weights, part of my head or shoulders, depending on position will be at or very near the surface. Exhale = sink. ( all water bodies, types, that I have been in.)
Longest stretch in water without any gear and no bottom, 4 hours.
Except in extreme cases, water survival is about mind set, not abilities.
(faulty tank and regulator left me with half a breath at 130 feet.) {dump belt, inflate BC and focus, focus, focus.} (dive buddy assigned to me was not paying attention, night dive and was behind me and turned off in some other direction) (fresh water)
YMMV
That’s me also. Air in the lungs, legs slowly sink but I might just be able to keep enough topsides to breathe, if the water was still. Empty lungs, dragged to the bottom by my legs. Happens now when I’m 70kg as it did when I was 99kg.
Another anecdote:
I was obese for the biggest part of my life, 160-170 kg. I never had problem floating in water whether it was salt water or fresh water. I could simply stay perfectly still and I would float.
Then I started losing weight. When I reached around 130kg the flotation problem became apparent. That is, I would still float, but while previously the water line stayed well below my chin, now it raised at chin level. If I expelled my breath I would start sinking.
Today I am 100kg and I cannot float at all. I have to move my arms constantly to stay afloat, else I sink. In fresh water it is even worse, I have to move my hands so vigorously to stay afloat that I get tired after a while.
I can’t imagine what will happen when I reach the more ideal 80kg weight
I can but only if I’m on my back. If I’m not, then I have to keep moving.