Lochjaw

From the instruction manual:

You are a deep sea diver in search of a fabulous treasure of diamonds from the hold of a Spanish Galleon that sank during a fierce storm in the early sixteenth century. You dive deep into the murky darkness of Davey Jones' Locker, and enter the shark-infested maze of kelp to retrieve the treasure. You know the mission is rife with danger...the menace of the man-eating sharks that patrol the kelp beds...the lurking menace of the legendary Loch Ness monster, a beast that will pursue you relentlessly if you dare invade its territory.