True Grandpa, lean folk sink much easier than us chubby bobbers. I knew a few really lanky fellows in the Army that would go straight to the bottom like a lawn dart. Also, it's easier to float in salt water than fresh, believe it or not. I also think a lot of has to do with confidence in the water, some don't know how their body reacts in water and tend to panic a little. Getting in a nice deep pool and practicing floating on your back. This will help build some confidence and take some of the fear away knowing that you are able to at least float on your back.