Interesting game, personally I couldn't really figure out what to do even after reading the description. I didn't really understand how build the ship effectively to dive into the ocean and reach the top secret box. And having the hold C + press L trick to gain money didn't feel rewarding; I guess this is technically a debug tool, so that could explain it. One other minor nitpick would be not being able to view an item description in the shop, you have to buy it and check it, then re-sell it if you don't want the item; hovering over the item would be a good way to show the item description.
This is super ambitious though, making a ship-builder game, so great job on the submission!