Sea Serpents

Massive sea dwelling creatures living in the seas in Narnia, sea serpents seem to be generally hostile to seafarers. The Dawn Treader and it's crew encounter a sea serpent on their voyage in search of the seven lost Lords of Narnia. It coils itself around the ship, seemingly in an attempt to break it in two (otherwise it may have just entangled itself with the ship in an exceedingly idiotic fashion). Due to the serpent's extremely strong hide, swords were useless against it, and only by following Reepicheep's advice to push the coiled body over the side of the ship, were they saved.