A person who don't know how to swim goes in river. but after sometime he or she get sink into the water and the dead body of that person get float or remain submerged on the water as he is died. is the buoyancy(upthrust) in that water makes the body float on the water after death? but when that person was trying to swim in water got sinked in water after sometime. does the buoyant force was acting on that body when the person was trying to swim but get sinked?