I've experimented with this. If I exhale, I sink. My body fat percentage is somewhere around 20%. I estimate that I need at least 1/3 to 1/2 a lung-full of air to have even neutral buoyancy. I understand that I might be unusual in this.
My body fat percentage is somewhat lower than yours, but my experience is similar. Actually, I have to swim moderately vigorously to keep my face out of the water, even with full lungs. A pool activity I enjoy is laying on the floor with swim goggles, watching the water surface from below.
Ever tried blowing bubble rings? It's not too hard, but it takes a bit of work to make good ones (and good capacity & patience, swirling water destroys them).
Same here, and I suspect your upvotes are from others who can sink.
One of the ways I have fun in the water is to breathe a good amount of my lungs out, and sit on the bottom as long as I can. Sit, not hold-by-swimming. It's an incredibly effective way of learning how to control your heartrate & panic response to holding your breath, because it's hardly possible without control, and then it's pretty darned easy.
Hehe, that's I game I loved to play when I was a kid (ok, I admit, I still like it today). Never occurred to me that bodyfat could have something to do with it. And I agree it's an amazing feeling, maybe we could start an underwater meditation club? ;-)
