Tony Wu / Humpback whale (Megaptera novaeangliae australis) male calf playing at ocean surface after coming up to breathe. Vava'u Islands, Tonga.

Gary Bell/ Oceanwide / Oriental Flying Gurnard (Dactyloptena orientalis) with pectoral fins extended in defense posture, Anilao, Philippines

Tony Wu / Humpback whale (Megaptera novaeangliae) lying on its side while executing a series of pectoral fin slaps on ocean surface. Vava'u, Tonga, South Pacific.

David Fleetham / Humpback whale (Megaptera novaeangliae), mother and calf swimming just below surface in front of the West Maui Mountains. South of Lahaina, West Maui, Hawaii.

Espen Bergersen / Humpback whale (Megaptera novaeangliae) with fin above water, Andfjorden close to Andoya, Nordland, Northern Norway. January.

Chris & Monique Fallows / Orca male (Orcinus orca) raising pectoral flipper out of the water, Prince William Sound, Alaska, USA.

Jeff Rotman / Pectoral fin of a Steepheaded parrotfish (Chlororus gibbus) in the Red Sea, Egypt.

Norbert Wu / Flying Fish (Exocoetidae) uses large pectoral fins to glide through the air, Saba Island, Dutch Antilles

Gabriel Rojo / Southern right whale pectoral fin {Balaena glacialis australis} Patagonia, Argentina

David Hall / Blackfoot firefish (Parapterois heterurus), blue stripes on pectoral fin when threatened, on gravel. Pantar, Alor Archipelago, Indonesia.

David Hall / Blackfoot firefish (Parapterois heterura), blue striped pectoral fins displayed as a response to threat. Pantar Island, Alor Archipelago, Indonesia.

Felis Images / Fisherman removing Shark (Elasmobranchii) pectoral fins. Negombo Fish Market, Sri Lanka. 2017. Photo Vydhehi Kadur/Felis Images