The Zuiyo-maru carcass was a corpse, caught by the Japanese fishing trawler Zuiyō Maru (瑞洋丸) off the coast of New Zealand in 1977. The carcass's peculiar appearance resulted in speculation that it might be the remains of a sea serpent or prehistoric plesiosaur.

The basking shark is the second-largest living shark and fish, after the whale shark. It is one of three plankton-eating shark species, along with the whale shark and megamouth shark. Typically, basking sharks reach 7.9 m (26 ft) in length. It is usually greyish-brown, with mottled skin, with the inside of the mouth being white in colour. The caudal fin has a strong lateral keel and a crescent shape. Other common names include bone shark, elephant shark, sailfish, and sunfish. In Orkney, it is called hoe-mother, meaning "the mother of the picked dogfish".