Certain species of fish and birds are able to locomote in both air and water, two fluid media with very different properties. A fluid is a particular phase of matter that deforms under shear stresses
Penguins swim by "flying" beneath the surface of the water.
Flying fish use their pectoral fins to glide above the water's surface.
Boxfish are the classic biological example of MPF swimming because they are not well streamlined and use primarily their pectoral fins for thrust production.
Puffins both swim and fly using lift produced by their wings.
Flying fish
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The Exocoetidae are a family of saltwater ray-finned fish in the order Beloniformes, known colloquially as flying fish or flying cod, with about 64 species in seven genera. While they do not "fly" in
Dried flying fish for sale in Tokyo
Sushi with tobiko, or flying fish roe