In folklore, a mermaid

Is an aquatic creature with the head and upper body of a female human and the tail of a fish. The male equivalent of the mermaid is the merman, also a familiar figure in folklore and heraldry. The conception of mermaids in the West may have been influenced by the Sirens of Greek mythology, which were originally half-birdlike, but came to be pictured as half-fishlike in the Christian era. The conception of the siren as both a mermaid-like creature and part bird-like persisted in Byzantine Greece for some time. There is a modern Greek legend that Alexander the Greats sister Thessalonike did not die and turned into a mermaid after her death, living in the Aegean. She would ask the sailors on any ship she would encounter only one question: "Is King Alexander alive?", to which the correct answer was: "He lives and reigns and conquers the world". This answer would please her, and she would accordingly calm the waters and bid the ship farewell. Any other answer would enrage her, and she would stir up a terrible storm, dooming the ship and every sailor on board.

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