• (a.) Inclined or adapted to swim; swimming; as, natatorial birds. • (a.) Inclined or adapted to swim; swimming; as, natatorial birds.
Na`ta·to'rial adjective Inclined or adapted to swim; swimming; as, natatorial birds. 
natant, natation, natatorial 1. The act or art of swimming or floating on water. 2. Adapted for swimming.
descriptive of swimming or adaptations for locomotion in water. This term is generally applied to swimming legs in subaquatic insects.
pertaining to, adapted for, or characterized by swimming: natatorial birds.