Very impressive submission given the timeframe. Well done for submitting a 2.5D game.
Visuals are very pleasent. Liked the glowing effect of the fish and exploring the depths like the cave. The music really added to the atmosphere too. The sound design in general was a strength, liked the nice touch of the music becoming slightly muffled when going underwater.
For improvements, I'd work on the performance. Quite laggy even on my decent PC. Maybe add another mechanic or two as well (a map of explored places, some upgrades to the ship, etc.)
Also its generally a bad idea to submit a downloadable game that is 400MB download and 2GB unzipped in a Game Jam ;)
Cool submission. Lots of potential for the future if you so choose to continue working on it. Good job!