Sure it does. Look it up.
Your idiocy?
DU?
MoveON?
Humor me. show me a link to a claim that the water displaced by an immersed human body measures weight, mass and body fat.
I'm willing to accept the possibility that body fat can be estimated by comparing weight (measured independently) and body volume. But that isn't what you are claiming.
I would like to see a reference to a procedure that measures the weight of a human body by displacing water.
By the way, do you claim that gravity cannot be directly detected?