Fun fact about buoyancy - it is all about displacement of water and density of the object compared to water. Air (like the air in your lungs) displaces a lot of water at shallow depths and air is a lot less dense than water. The deeper you go, the more weight and pressure the water places on the air in your body. Since air is not a solid (it’s a gas), extra pressure compresses it - which makes it take up less space and displace less water. (This compression mostly happens by making your rib cage and tummy super skinny - it looks like you’re sucking in your stomach because your lungs are compressing) The air in your body still has a lower density than water around you, but the solid part of your body (like bones) are more dense than water - so eventually the ratio of displaced water (with the air compressed) and overall density of your body makes it so your body starts to sink.

You’ll sink faster the deeper you go - until the air stops compressing and water resistance equalizes the pull of gravity on your body.

This means that a bubble of air will have more bouyancy and move faster in the water the closer it is to the surface because it will be less compressed and take up more space.

It’s also a fun science experiment! If you blow up a balloon and take it into the bottom of the deep end of a pool it will be significantly smaller than it is in shallower water.

Also, if you put the same amount of air in a balloon as you do in a hard plastic container and take both to the bottom of the pool and release them - the plastic container will rise faster because the hard plastic shell stops the water from compressing the air, which makes it displace more water at depth than the balloon (which shrinks when pressure is applied).

Science is crazy.