Exploring the harbor of San Juan in Puerto Rico and you notice an old man pottering around on a mysterious vessel. As you get nearer, he greets you and tells you about his homemade submarine. He built it, he says, to be able to hunt for sunken wrecks in this area. Sadly, he is now too old to take the submarine down himself. When he offers you the opportunity to take a dive you excitedly agree. You listen as he quickly explains how everything works, you get on board, and dive down.

Very soon after diving below the surface, something goes wrong: the old boat breaks down and you sink, out of control, to the seabed. The main pressure line has blown and the engines have stopped running. What will you do to survive? Piece together the 759 pieces and solve the riddles to save your life!