Do fat people float better than skinny people?

It would depend if it is really fat or muscle. If it is fat, then it is actually oil, and oil is less dense than water and floats. (Just try pooring olive oil in a glass). However, muscle, bone, and other tissues are either denser than water or not less dense enough to have much boyancy. Since it's really density, not weight, that matters, it also makes a difference how much air is in the floater's lungs. Lastly, it depends on the water. In the salt-rich Dead Sea, for example, basically everyone can float. But in some areas with desolved gas, such as the Bermuda Triangle, sudden changes in density had been known to even sink ships. In a nutshell: You float if you are less dense (density=weight/volume) than water, or another fluid. Fat will make you less dense, muscle is hevier then fat and will either not help or make you sink more.