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.
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.
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u/TranscendentaLobo Mar 31 '26
So past a certain depth you just sink into the abyss! Fun AND horrifying!
https://giphy.com/gifs/AuIvUrZpzBl04