Wing-propelled diving

Wing-propelled diving is underwater locomotion in which an animal generates thrust by flapping its wings. It is used by birds such as penguins, auks, and diving petrels.

Underwater flight: Locomotion through water using repeated wing strokes that generate lift and thrust. The motion resembles aerial flight, but water resistance changes how each stroke produces thrust.
Penguin: A flightless seabird whose wings are adapted into flippers for swimming. Penguins are the clearest specialists in propulsion by flapping wings beneath the surface.
Foot-propelled diving: Underwater locomotion in which a bird generates thrust mainly by paddling with its feet. It contrasts with wing strokes as the principal source of underwater thrust.
Wing loading: The ratio of an animal's weight to the area of its wings. Wing dimensions balance the demands of moving through dense water and, in some species, flying in air.
Hydrodynamics: The study of fluids in motion and the forces they exert on objects. Water’s density and viscosity determine the forces acting on wings and bodies during dives.
Auk: A seabird in the family Alcidae, including puffins, murres, and razorbills. Auks retain aerial flight while using their wings to pursue prey underwater.
Cormorant: A fish-eating waterbird that pursues prey underwater mainly with its feet. Cormorants exemplify the foot-powered strategy used by many pursuit-diving birds.
Foraging ecology: The study of how animals search for, obtain, and use food. Propulsive capacity influences which prey divers can pursue and how they exploit marine habitats.
Buoyancy: The upward force exerted by a fluid on an immersed object. Air trapped in plumage and lungs assists ascent but makes descent more costly.
Diving petrel: A small seabird in the family Pelecanoididae that dives and swims using its wings. Diving petrels show how compact wings support underwater propulsion in small seabirds.

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