Puzzle 759 Submarine

For several days you have been on a luxurious cruise through the fairy-tale Caribbean islands. At the moment, the ship is anchored in the port of San Juan in Puerto Rico, and you disembark to explore the harbor. Away from... the crowd, you notice an old man fiddling with a strange vessel. As you approach, he greets you and tells you about his homemade submarine. According to him, he built it to be able to search for shipwrecks in the area. Unfortunately, he is now too old to launch the submarine by himself. When he offers you to try diving instead of him, your adventurous spirit awakens, and you gladly agree. You listen as the old man quickly explains how everything works, board the vessel, and dive down. Very shortly after diving underwater, something goes wrong: the old boat breaks down, the situation spirals out of your control, and you sink. The main pressure line has burnt out, and the engines have stopped working. What now? How can you fix the breakdown? Will you be able to find the necessary parts in all this mess and confusion to repair the engines and resume operation of the submarine? Or will you meet a tragic end here, becoming food for sharks?
The packaging contains a puzzle of 759 puzzling pieces, a set of instructions in different languages, and an envelope with answers.
Difficulty level 4.