Answer: seaserpent

AnswerCrossword Clue
SEASERPENTPirate-tale beast
SEASERPENTLegendary swimmer
SEASERPENTCryptozoologist's quarry
SEASERPENTWhat the constellation Hydra represents
SEASERPENTImaginary snakelike swimmer
SEASERPENTMythological swimmer
SEASERPENTRelative of Loch Ness monster.
SEASERPENTDenizen of Loch Ness.
SEASERPENTHydra
SEASERPENTCecil of cartoons
SEASERPENTHydra, astronomically
SEASERPENTMysterious swimmer
SEASERPENTImage on many an old map
SEASERPENTLegendary denizen of the deep
SEASERPENTImage on an ancient mariner's map