It's not an adventure until you're totally submerged!
Our first priority here should be finding the sunken boat.
Unlike normal walkthroughs, in Nice Game Hints you can select just the puzzle you want hints for. Here are listed the puzzles for "On the bottom of the lake" in Dexter Stardust: Adventures in Outer Space. The guide you choose only contains information about that puzzle, reducing possible spoilers for other puzzles.