1) Legendary turtle 
According to the tradition of the Physiologus and medieval bestiaries, the aspidochelone is a fabled sea creature, variously described as a large whale or vast sea turtle, and a giant sea monster with huge spines on the ridge of its back. No matter what form it is, it is always described as being huge, often it is mistaken for an island and appear...
Medieval Bestiaries) - A gargantuan whale or sea turtle that would trick sailors to landing on its back, then drown them. Snap.