I LOVE this game! It has such a cozy yet exotic vibe to it. I think it would be really cool if you played a little bit more with light, since we are in a submarine, after all. Having a little light attached to the submarine to add to the feeling of exploration would be really radical. Also, maybe it's my mouse or maybe it's just classic unity webgl shenanigans, but the mouse seems a bit sensitive.
Also, possibly some sort of visual/audio feedback for when we speed up/slow down would be great, because some times I didn't notice if I was actually moving faster.