The Megaladon chases and chomps and the Kraken traps and constricts. What if there was an AI threat that brought the best of both worlds. It can take the Jaws like experience of the Megaladon by dipping below the water and popping up to take a bite out of your ship, and it could wrap around the ship and snatch crew members off the deck like the Kraken does.

Just imagine sailing and minding your own business, and at the wheel you see a shadow under the water dart from port to starboard beneath the ship. You're ship is still moving and the water's not black so not the Kraken. No need to panic you keep sailing. A few moments later a serpent shoots out of the water and flys over your ship before disappearing back under the waves. Thus beginning the Sea Serpent ecounter.