# How fat do you have to be to float withot effort? **URL:** \ **Category:** Factual Questions\ **Created:** [November 27, 2013, 5:50pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933 "2013-11-27T17:50:19Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Artemis\_Tardis](https://avatars.discourse-cdn.com/v4/letter/a/4bbf92/32.png) [@Artemis\_Tardis](https://boards.straightdope.com/u/Artemis_Tardis)\ **Post date:** [November 27, 2013, 5:50pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/1 "2013-11-27T17:50:19Z")
When I was at school we used to joke that if there was a flood (our school was right besides a road that ran over a river that overflowed sometimes due to rain) we would have to grab the school’s principal, as she was quite… large, so she would float. I was wondering now - how fat does one have to be to be able to float, let’s say, after a ship wreck? Ignore clothing, drag from the sinking ship, wind, etc. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [November 27, 2013, 5:53pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/2 "2013-11-27T17:53:12Z")
Most people can float just fine, even skinny people. The problem is that you will tend to float face down in the water if you don’t put any effort into keeping your head in a position that allows you to breath. That gets tiring and requires you to stay focused which can be hard to do for long periods. ---
**Author:** ![Mr.Excellent](https://avatars.discourse-cdn.com/v4/letter/m/f19dbf/32.png) [@Mr.Excellent](https://boards.straightdope.com/u/Mr.Excellent)\ **Post date:** [November 27, 2013, 6:42pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/3 "2013-11-27T18:42:35Z")
Also depends upon the salinity of the water - it’s slightly easier to float in the ocean than in a freshwater lake, and _much_ easier to float in the Dead Sea. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [November 27, 2013, 6:49pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/4 "2013-11-27T18:49:22Z")
> [@Shagnasty](#): > > Most people can float just fine, even skinny people. The problem is that you will tend to float face down in the water if you don’t put any effort into keeping your head in a position that allows you to breath. That gets tiring and requires you to stay focused which can be hard to do for long periods. With a height of 186 cm and a BMI at the very lowest end of normal I used to have negative buoyancy unless my lungs were filled to the max. If I let my breath out I would sink like a thing with significant negative buoyancy. I’m now more comfortably in the normal BMI range, though still skinny by most standards, and although I haven’t really thought to test my buoyancy lately I suspect I now float just fine, so you “Most people” is probably accurate. I just wanted to make it clear that really skinny people sink. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [November 27, 2013, 7:03pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/5 "2013-11-27T19:03:30Z")
At 165# I had a lot of trouble floating even in the ocean, at 200# I can lay on my back and actually go to sleep while floating in the ocean. Really not that much difference in weight made a big difference in my bouancy. ---
**Author:** ![JerrySTL](https://avatars.discourse-cdn.com/v4/letter/j/e274bd/32.png) [@JerrySTL](https://boards.straightdope.com/u/JerrySTL)\ **Post date:** [November 27, 2013, 7:10pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/6 "2013-11-27T19:10:13Z")
> [@Mr.Excellent](#): > > Also depends upon the salinity of the water - it’s slightly easier to float in the ocean than in a freshwater lake, and _much_ easier to float in the Dead Sea. I was 6’1" and 170 lbs when I swam in the Great Salt Lake years ago. I think I would have needed to be holding at least a 10 lb rock to stay fully under water. ---
**Author:** ![rhubarbarin](https://avatars.discourse-cdn.com/v4/letter/r/eb9ed0/32.png) [@rhubarbarin](https://boards.straightdope.com/u/rhubarbarin)\ **Post date:** [November 27, 2013, 7:24pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/7 "2013-11-27T19:24:35Z")
I float almost effortlessly on my back. I’m very thin (BMI 17) but all my fat is in my hips, so they float, and my upper body is so light that it seems all I need to do is breathe to keep it buoyant. I’m pretty sure could sleep in the water on my back. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [November 27, 2013, 7:52pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/8 "2013-11-27T19:52:14Z")
The only place I’ve ever been able to float is the Adriatic . I’m 175, 5’11", but unless I take a deep breath and hold it, I sink in fresh water. ---
**Author:** ![Artemis\_Tardis](https://avatars.discourse-cdn.com/v4/letter/a/4bbf92/32.png) [@Artemis\_Tardis](https://boards.straightdope.com/u/Artemis_Tardis)\ **Post date:** [November 27, 2013, 8:00pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/9 "2013-11-27T20:00:45Z")
> [@naita](#): > > With a height of 186 cm and a BMI at the very lowest end of normal I used to have negative buoyancy unless my lungs were filled to the max. If I let my breath out I would sink like a thing with significant negative buoyancy. > > I’m now more comfortably in the normal BMI range, though still skinny by most standards, and although I haven’t really thought to test my buoyancy lately I suspect I now float just fine, so you “Most people” is probably accurate. I just wanted to make it clear that really skinny people sink. It is curious that I am 177 cm and I weight only 55 kgs, so my BMI is also quite low… and I can’t dive to the bottom of a swimming pool. And if I lay on my back I can float pretty easily on a pool. The only thing is that I have to hold my head upright, otherwise it sinks, so I don’t think I could sleep while floating without drowning. ---
**Author:** ![Icarus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/icarus/32/72_2.png) [@Icarus](https://boards.straightdope.com/u/Icarus)\ **Post date:** [November 27, 2013, 8:45pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/10 "2013-11-27T20:45:17Z")
Just one data point - I had an aunt who was around 300 lbs. She would float in freshwater, with her head clearly above the waterline. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 27, 2013, 10:42pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/11 "2013-11-27T22:42:49Z")
I was extremely thin when young and floated with ease. A lot of factors other than fat come into play. I am still thinnish and still float well, of course. People at the pool comment on it. I don’t see what’s so magic about it. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [November 27, 2013, 10:46pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/12 "2013-11-27T22:46:59Z")
I’ve never been able to float well. Whenever I try, my legs and hips want to sink, which will pull me down and flip me over face down. This for a range of weights from 125 lbs to 220 lbs at essentially the same height. If I could get my legs/hips to float, my upper body floats fine. Though my head might bob below the water level if the water isn’t very still. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [November 28, 2013, 12:05am UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/13 "2013-11-28T00:05:00Z")
I have always, since I was a child, been able to float flat on my back in the sea and in swimming pools. In fresh water I do have to keep my lungs fairly full, but it causes me no problems. ---
**Author:** ![sisu](https://avatars.discourse-cdn.com/v4/letter/s/df705f/32.png) [@sisu](https://boards.straightdope.com/u/sisu)\ **Post date:** [November 28, 2013, 12:38am UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/14 "2013-11-28T00:38:21Z")
I have always been able to float just fine, the problem is that I keep flipping onto my stomach. If you do need to float for long periods then accept natural buoyancy and use very small movements to keep you facing the right way. ---
**Author:** ![Chimera](https://avatars.discourse-cdn.com/v4/letter/c/8e8cbc/32.png) [@Chimera](https://boards.straightdope.com/u/Chimera)\ **Post date:** [November 28, 2013, 12:46am UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/15 "2013-11-28T00:46:37Z")
5’11" Running anywhere from 205 to 240 over the last 10 years, at the heavy end I have no issue floating in fresh water. At the lower end it takes a small amount of effort. I can swim easily on my back using only my arms or only my legs. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [November 29, 2013, 3:24am UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/16 "2013-11-29T03:24:26Z")
See, I was a pretty chubby kid, making it to 200+ pounds at one point. But I had horrible trouble floating. My legs and butt would float, but only if I held on to something for the rest of me. And even though I would go underwater, I stayed upright, so it wasn’t just my head being tilted down. But I have always been told that I look a lot less heavy than I am. So maybe I’m more dense for some reason. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [November 29, 2013, 5:27am UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/17 "2013-11-29T05:27:16Z")
Female, obese, big ass and thighs and bigger rack: at any size, even as a teenager with Marilyn Monroe’s measurements, I floated with very little effort. Sure, I had to focus to keep my hips tight and get my pelvis parallel to the surface of the water, but once I got the booty up there, no more effort was required. At 200 pounds, I can float in a cross legged sitting position with my head above the surface - my boobs act as a lifevest. Maintaining my position takes a little bit of awareness, but I can “sit” in the water and talk with you and you’d swear I was sitting on a float a couple of feet under the surface. At 250 pounds, it took a lot of effort to keep my arms and legs under the surface of the water at all. Like, a \*lot \*of effort. I’d have to keep my feet on the bottom of the pool and my knees locked to keep my legs from slipping out from under me and tumbling me arse over teakettle and dunking my head. My dad, also obese and clearly of the same genetic tree (I look more like his side of the family than mom’s) can sit at the bottom of the pool or ocean with a lungful of air. Can’t figure that one out. Man’s got a good deal of fat on him, particularly on the belly, but he’s dense enough overall to sink. ---
**Author:** ![LinusK](https://avatars.discourse-cdn.com/v4/letter/l/258eb7/32.png) [@LinusK](https://boards.straightdope.com/u/LinusK)\ **Post date:** [November 29, 2013, 6:11am UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/18 "2013-11-29T06:11:46Z")
My swimming teacher in HS insisted “everybody” floats, when she tried to teach the deadman’s float. Didn’t work for me, unless I treaded water at least a little bit. Without my lungs completely full of air, I sink like a stone. ---
**Author:** ![Shakester](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/shakester/32/437_2.png) [@Shakester](https://boards.straightdope.com/u/Shakester)\ **Post date:** [November 29, 2013, 11:13am UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/19 "2013-11-29T11:13:59Z")
I’m 180 cm and around 60 kilos; skinny. I do not float, I sink like a rock. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [November 29, 2013, 2:22pm UTC](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933/20 "2013-11-29T14:22:26Z")
So all this tells us the GQ answer seems to be “it depends …” Interestingly the biggest difference might not be how much fat, or even where the fat is, or even how much muscle. Skeletal variation probably matters more. Bones are the most [dense human tissue](http://www.scrollseek.com/training/densitiesofdifferentbodymatter.html) by far. > [@](#): > > Type Avg Density Value (g/ml) > Blood 1.0428 g/cm3 > Bone 1.7500 g/cm3 > Fat 0.9094 g/cm3 > Muscle 1.0599 g/cm3 [Next page](https://boards.straightdope.com/t/how-fat-do-you-have-to-be-to-float-withot-effort/674933.md?page=2)