Buoyancy in the water

[mike0318sti]

I couldn't find any info on this. Anyone have any issue with staying down when underwater? I notice some people can go under and have no problem staying on the bottom and others have to fight to stay down. Is it just body type that determines this, or is there something they are doing different? The reason I ask is because on the pool comp in the BUD/S videos, it doesn't look like they have a weight belt on, and none of them seem to have to try to stay down once they take off the scuba tanks. Thanks.

[oldswabbie]

I couldn't find any info on this. Anyone have any issue with staying down when underwater? I notice some people can go under and have no problem staying on the bottom and others have to fight to stay down. Is it just body type that determines this, or is there something they are doing different? The reason I ask is because on the pool comp in the BUD/S videos, it doesn't look like they have a weight belt on, and none of them seem to have to try to stay down once they take off the scuba tanks. Thanks.


Ask DDSSDV ~ I can guarantee you he will know the answer having been a Navy Diver. Ps...I'd like to know too!


OldSwabbie

[jamaisenbach]

Buoyancy has a lot to do with the air in your lungs. Try this when you are in the pool. Jump in the deep and take a deep breath trying to pull in all the air you can and hold it. You should float up at the top or at least only sink a little bit. Slowly let out a little bit of air and you will feel yourself sinking until you hit a point in the water where you stop. Keep doing this until you reach the bottom. The key is to release just enough air from your lungs to keep you down without letting it all out.

This can also help out with treading water; keep your lungs filled with air to help keep you buoyant.

Swimmers usually have a very low body fat % but use this to keep themselves buoyant when they need to.

[bigv123]

Muscle tissue is more dense than water...hence, guys with low body fat % tend to sink more easily than those with higher body fat %. Conversely, fat tissue has a very similar density to water due to its composition, hence those high body fat% tend to float more easily. Also, I'm sure the amount (volume) of air you hold in your lungs while underwater affects your buoyancy as well.

DFC will probably have much more detailed info.

V

[oldswabbie]

DFC will probably have much more detailed info.

V

Yea, I PM'd him and told him about this thread, said it was something he probably had the answer to. But I think you are correct (from what I've read)

:)

OldSwabbie

[ddssdv]

Almost. Its bone density. Some fat folks can stay down without assitance and some skinny or low body fat folks fight to stay down. Its all in your bone density. Bones are like cork and some people have less dense bones than other and will float like a...well cork. It jus how you waz made mate. Try taking less air in your lungs and release some when you are at depth. Yes...you won't stay down as long but you may get the job done.

[ndriddle]

BigV123 is the most accurate in his answer to your question. Your muscle mass compared to fat mass has the most to do with your buoyancy in water when the air is expelled from your lungs as jamaisenbach had to say.. That is the reason underwater weighing is by far the most accurate prediction of your body fat compared to any other way of assessing body fat like the bod pod or body fat calipers.

[ddssdv]

Yeah I agree but I know some food blisters who sink like rocks and a tri athelete you floats like a cork.

[oldswabbie]

Yeah I agree but I know some food blisters who sink like rocks and a tri athelete you floats like a cork.

Ndriddle, I've gotta go with Dave on this. Now that I think about it (I was wrong in my earlier post), I've also seen the same thing in pools/ocean etc. I stand corrected. Dave was a Navy Diver for a long, long time. This is one thing he definately knows and knows very well.


OldSwabbie

[honorman]

I couldn't find any info on this. Anyone have any issue with staying down when underwater? I notice some people can go under and have no problem staying on the bottom and others have to fight to stay down. Is it just body type that determines this, or is there something they are doing different? The reason I ask is because on the pool comp in the BUD/S videos, it doesn't look like they have a weight belt on, and none of them seem to have to try to stay down once they take off the scuba tanks. Thanks.

fyi...you do use weight belt's in pool comp!! in fact the last thing you do before kissing the pool and fsa'ing....is throw your weight belt over your tanks...many a guy a failed pool comp cuz they forgot their weight belt and fsa'd with their belt still on them!!

[MrParker]

Almost. Its bone density. Some fat folks can stay down without assitance and some skinny or low body fat folks fight to stay down. Its all in your bone density. Bones are like cork and some people have less dense bones than other and will float like a...well cork. It jus how you waz made mate. Try taking less air in your lungs and release some when you are at depth. Yes...you won't stay down as long but you may get the job done.

Ddssdv has it right...so does BigV, muscle tissue and fat are also part of the puzzle. I am a big guy, 215...no more then 10% body fat, I float like a cork. When I trained for BUD/S I was 175 and less then 9% body fat, float like a cork, when I raced bikes I was 172lbs, 6% body fat, float like a cork. My good friend that trained with me...5'6 150 lbs, body fat probably around 7-8%, sank like a rock. Even after he added some fat, sank like a rock. Use your lungs to adjust your bouyance like was already mentioned.

[mike0318sti]

Thanks, I'll work on holding less air before I go down from now on. It was hard to see the Dive belt on the video I looked at online. Thanks for everyones input.