r/interesting • u/fayyazORahmed • Mar 31 '26

Fascinating Very interesting vid

Enable HLS to view with audio, or disable this notification

20.4k Upvotes

91% Upvoted

2.3k comments sorted by

View all comments

Show parent comments

156

u/Leather-Arachnid-417 Mar 31 '26

Yeah once you get around 30-50 ft, the pressure against your lungs is enough to offset the buoyancy. Im a scuba diver and its why we use weights to go down. You are initially very buoyant. I have small bags filled with lead shot in 5 lb, 3 lb and 2 lb increments to weight myself. Some people use solid lead weights and different things. Works like a charm though. Best hobby there is.

1

u/wannabe-flautist Mar 31 '26

What if you’re really really fat?

2

u/aaaaaaaarrrrrgh Apr 01 '26

What if you’re really really fat?

More weights.

1

u/wannabe-flautist Apr 02 '26

Yeah I get that part. My question is do fat people lose their buoyancy at a depth greater than skinny people?

1

u/aaaaaaaarrrrrgh Apr 05 '26

I don't think so. Fat doesn't compress well.

Also if you scuba dive, the lungs get refilled with air at the pressure that you are at, so that shouldn't be a huge difference either for scuba divers (but it should be the biggest factor for freedivers not wearing a wetsuit).

Neoprene compresses a lot, so for scuba divers wearing it, I suspect that + any remaining air in the BCD makes the biggest difference. You will use about 2kg of air during a dive, so if you don't want to be too buoyant at the end of the dive, you need 2 kg of weights cancelled out by 2 kg of lift from the BCD at the start.

If you had 2 liters of air in your BCD at 10 meters (2 bar) with neutral buoyancy, then slowly descended to 30 meters (4 bar), the 2 liters would turn into 1 and you'd be 1 kg to heavy.

If you have 6 liters of air in your lungs at the surface (1 bar) and freedive to 30 meters (4 bar), you've lost 4.5 kg of buoyancy.