I enjoyed your game, I really think you did a good job with the sonar mechanic. and I particularly love that you added little effects to the ship when you did something, like speeding up = pulled the lever up.
some notes I would make is adding some sound or perhaps some moving obstacles to keep the player engaged. It also took me a while to figure out how to start again after i stopped the boat. But otherwise with some polish it could prove to be quite promising :)