Really like the art style. Could see my patience being tested, and I had more fun when I slowed down the pace. The most innovating part was the octopus hiding in the chest. It keeps you on the edge.

Some minor nitpicks:

- The movement where the submarine follows the mouse click is well done, especially rotating the sub.
- I found it bit cumbersome to right-click on the mouse though. The browser somehow opens another tab or glitches out even in full-screen mode.
- I was a bit puzzled when the engine sound was completely cutoff when the submarine stops. Also it could be cool to see it decelerate while stopping.
- Would love to see subtle parallax effects with the background layers as the player goes deeper.