people most certainly don't have the same density. If your body fat is <10% you will not easily float in water, whereas if you're 30%+ you're basically an inner

people most certainly don't have the same density. If your body fat is <10% you will not easily float in water, whereas if you're 30%+ you're basically an inner tube. However that is beside OP's point. Someone like Lebron James is not overweight but it's entirely possible he would need to buy two tickets.