You are a diver in an underwater maze. Throughout the maze are valuable diamonds, and your goal is to retrieve as many as you can. In the middle of the screen is a shark cage where you begin. As you collect diamonds you need to bring them back to the shark cage in order to earn points. Swimming back and forth constantly is a deadly shark. If the shark encounters any of the diamonds, it will eat them; likewise you can also be eaten by the shark, causing you to lose a life. You have no defense against the shark, however you are immune if you are in the shark cage and the doors are closed. Somewhere in the maze the Loch Ness monster remains hidden. If you disturb the monster, it will continuously chase you unless you can lead it back into one of the caves located in the corners of the screen.

This game's name was changed from Lochjaw to Shark Attack because, being the game was about an attacking shark, there was a lawsuit that the game's name was too close to the movie title Jaws.