Natation :: Natation (n.) The act of floating on the water; swimming.
Supernatation :: Supernatant (n.) The liquid remaining after solids suspended in the liquid have been sedimented by gravity or by centrifugation. Contrasted with the solid sediment, or (in centrifugation) the pellet..
Transnatation :: Transnatation (n.) The act of swimming across, as a river..