Floating is a natural human capability that stems from being subtly less dense than water. The lungs, gut, and a layer of fat under the skin all help to make sure that most people don’t sink. Nature has also compensated for us not making bearing children obvious by providing a way for us to visibly prove our fertility–by actually floating!
The gas in a human’s body causes it to float. Bodies are made up of about 78% water, so the density is close to that of water. When a person sinks, they’re usually wearing significant amounts of clothing which lower their overall density and weight.
The key explanation has to do with the body’s ability to produce gas, especially when having just eaten (whether through swallowing air or by eating carbonated foods). So after swimming, breathing out more can make your body more buoyant which increases its mass below water. The equation for representing buoyancy goes as follows: ƨ=4gh/3πr²; where G= universal gravitational constant h= depth of water r= radius of object For every 10 feet you go under water.
Bodies rise for the same reason tires sinks in water, or submarines rise when they dive into the ocean. It’s all about how much air is inside something vs what it weighs on its own. A body is composed typically about 20% fat and feels very light if this fat has not been used as an energy source for your muscles or other organs during life then the amount of oxygen that can be deposed in a person’s tissues is.