Why do girls float better than boys?

Less muscle

also some girls are better swimmers than boys, more girls learn to float than boys. also maybe the girls you know are fat. fat floats and what that person said, less muscle, and less weight.

To be more specific, girls have a higher average body fat percentage than boys (a higher BMI). As fat is far less dense than muscle or bone, those with a higher BMI will float better than those with a low one. Scientifically, human fat has a lower density than water, while both human muscle tissue and bone have a density greater than water. A big cause of the difference between the two is the 5-10 lbs most girls' breasts weigh, vs the non-existent breast tissue in boys. Breast tissue is mostly fat and similar low-density flesh. For comparison, a top girl swimmer will have a body fat percentage of 8-10%, while a top boy swimmer will have 3-5% body fat.