What's typical buoyancy in just swim wear with no equipment?

[TSandM]

I've watched OW students do their treads for five years now, and I'm amazed at the range of buoyancy of a bathing-suit clad body. I have seen students who were nearly exhausted after ten minutes, because if they paused kicking for one moment, they instantly sank. I know from my own experience that I have trouble getting underwater even with empty lungs -- I float like a cork. It's the ratio of bone (which is negative) to fat (which is positive). A big-boned, muscular man with no body fat is going to be somewhat negative, and an osteoporotic woman carrying a few more pounds than she ought to is going to float.

Legs will always be more negative than the torso, for the fairly obvious reason that the torso contains relatively few bones and quite a bit of air.

 

[dmaziuk]

I found I float like a bobbing cork with my chest rising out of the water with a full breath. And about half way through exhaling I start to noticeably sink and towards empty lungs I sink like a stone. I can exhale and sit solid on the bottom of the pool. Hitting it with quite a thump if I wish.
My legs are also noticeably more negative than my torso.

So what is typical?

That.

 

[crunchiespg]

I've watched OW students do their treads for five years now, and I'm amazed at the range of buoyancy of a bathing-suit clad body. I have seen students who were nearly exhausted after ten minutes, because if they paused kicking for one moment, they instantly sank. I know from my own experience that I have trouble getting underwater even with empty lungs -- I float like a cork. It's the ratio of bone (which is negative) to fat (which is positive). A big-boned, muscular man with no body fat is going to be somewhat negative, and an osteoporotic woman carrying a few more pounds than she ought to is going to float.

Legs will always be more negative than the torso, for the fairly obvious reason that the torso contains relatively few bones and quite a bit of air.

Yes that was my impression of what is normal. However in my case I don't fit that profile. im a pretty stocky build, and normally pretty muscular. But I injured myself playing rugby and spent the last 18 months or so recovering from surgery. So I'm carrying a good 20lbs of extra weight.

But despite this I can float like a cork if I want to. Or I can sink like a stone. Everyone else I've spoken to seems to be one or the other.
The 15 min float is simple for me if I want it to be. But I can also deliberately make it hard by keeping my lungs more empty. Then I have to kick hard to stay afloat.
My guess is although I have the extra weight right now, underneath I've still got big bones and a decent muscle mass. Plus a big chest = big air capacity. So I can swing from one end of the scale to the other.

 

[tbone1004]

keep in mind that the average lung volume will hold approximately 5lbs of air, so that is a pretty substantial amount of buoyancy swing. More than enough to cause you to float or sink, the thing you have to be careful about when floating is making sure you do fully exhale because of CO2 buildup

Lynne, that effort you are seeing is a result of great inefficiency in their technique, not necessarily their mass. I sink, I can't float well on my back, certainly not without moving. I can however "tread" water with my ankles crossed and not get out of breath for >15mins. I can also tread water holding a standard 10lb diving brick for over 10 minutes without getting out of breath. That one is a technique issue, most people are horrible at treading water and most divers are abysmal at sculling at the surface so they get very out of breath but it is 100% technique, not their body composition.

 

[TSandM]

Well, some of the differences seem to correlate with how we end up needing to weight the students, so I do think there is a difference in body density. And obviously, a short, barrel-chested man is going to have a LOT of lung volume he can vary, and a short, small-framed woman will have far less buoyancy swing with breathing.

 

[jonhall]

The density of water is 1g/ml. Your body is around 60-75% water, so close to the same as water, therefore a person should float. Anything with a density of less than 1 will float, and more than 1 will sink. The saying, "fat floats, muscle sinks" was one of my favorites, and most of us, unless you are a lean, super athlete, have some fat. Go ahead and grab under your arm! Generally legs are more muscular because we walk and exercise them more. Also the 3 longest bones in the body are in your legs and bone is more dense than 1. Other things that make up our body also affect our buoyancy.


Also, "everyone floats, just not at the same level" is pretty much true. If you sink to the bottom of your pool, you weren't able to reach your floating level. Adults can be all over the place, but watch a baby, who is more water than an adult, they bob right to the top!


So air in the lungs will help us become more buoyant but your suit is probably a little more dense than 1.


Not sure if there is a typical buoyancy because we are all a little different….and wear different suits!


BTW, my upper body floats with a nice breath of air but my legs sink.

 

[Asteve]

Well if not everybody can not float, why is there a float test? I could see teaching a float skill. As a kid I could not float, swim out to the deep end, take a full breath and hold it, sink to the bottom. To pass the test I ended up putting my hands under me and fining them so no one could see me. Lived in the pool during the summer as a kid and would take swim lesson just to get in the pool a hour early. I was 5' 10" and 120 lb, now I am 80 lb more and have no problem floating. When snorkeling I wear 5-6 lb.

 

[TMHeimer]

Well, some of the differences seem to correlate with how we end up needing to weight the students, so I do think there is a difference in body density. And obviously, a short, barrel-chested man is going to have a LOT of lung volume he can vary, and a short, small-framed woman will have far less buoyancy swing with breathing.

Of course, I can confirm that. I sink. I tried every technique possible when faced with the 2 minutes "hands" out DM tread to end the 15 min. float. As I have said many times, only drown proofing worked.

---------- Post added May 22nd, 2015 at 05:20 PM ----------

Well if not everybody can not float, why is there a float test? I could see teaching a float skill. As a kid I could not float, swim out to the deep end, take a full breath and hold it, sink to the bottom. To pass the test I ended up putting my hands under me and fining them so no one could see me. Lived in the pool during the summer as a kid and would take swim lesson just to get in the pool a hour early. I was 5' 10" and 120 lb, now I am 80 lb more and have no problem floating. When snorkeling I wear 5-6 lb.

Why the test? Good question I have often asked. Why 10-15 minutes and not an hour in case your boat sank and you have no flotation device (it ALL sank?)--well that would take too much pool time. It has to do with what the purpose of any of these tests is. Is it to show technique? Body buoyancy? Strength/stamina? Or perhaps the favourite-- "comfortability in water"? One of those many discussed SB questions.

 

[Rich Keller]

I was playing around in the pool with my daughter today and having now got an appreciation to buoyancy from my diving I was figuring out my buoyancy in just swim shorts. I was also practicing the float skills for the divemaster course (along with trying to improve my 400m swim time)
But this got me thinking. What is typical for buoyancy?
I found I float like a bobbing cork with my chest rising out of the water with a full breath. And about half way through exhaling I start to noticeably sink and towards empty lungs I sink like a stone. I can exhale and sit solid on the bottom of the pool. Hitting it with quite a thump if I wish.
My legs are also noticeably more negative than my torso. Which is good as all my diving is in a dry suit and that makes them feel pretty buoyant so I'd hate it if my legs weren't so negative.

So what is typical?

You are typical of most people. There is a survival swimming technique based on this. You can stay afloat without moving at all using breath control alone. With a full breath you only exhale about half at a time and then breath in again with only your face staying above the surface. I used this technique while wearing all my scuba gear to get my weight exactly right before BCs were invented.

Drownproofing

 

[dmaziuk]

I sink, I can't float well on my back, certainly not without moving.

I can find the right balance point for floating on my back, but it's not easy to maintain it for very long. Moving definitely throws me off.

---------- Post added May 22nd, 2015 at 04:56 PM ----------

I could see teaching a float skill.

They do. I started swimming (as in sports) as a kid, one of the very few things I remember is they first had us do "bob" float followed by spreadeagle float on the front and back. Didn't teach swimming until we learned to float.