When I was a kid I would sink with a full breath of air (in a pool). I learned the back float and the dead man's float in swim lessons but I still needed to mov

When I was a kid I would sink with a full breath of air (in a pool). I learned the back float and the dead man's float in swim lessons but I still needed to move some water with my hands to stay on the surface. I enjoyed the fact that swimming in the ocean was easier since I didn't have to exert myself at all to float. Nowadays my BMI is such that I float in all bodies of water ;)