Cecil is correct. I have Xed a few. They are hard to eliminate. Usually even when shot (mortally but not yet dead) they go under and won't float up for a few hours. Some even dive down and bite on to or under limbs to stay down. Once in a while on a good shot they will flop around for a few seconds and then dive under. Once I saw a head shot with a rifle (243) that flopped once and stayed afloat.