Thank you!
I'm glad the swarm attack had the expected effect, I wanted it to be an element of surprise (see my answer to Dender46 for more detail).
Yes I also feel like this type of environment could definitely work well with some ambient sounds, I'd like to try adding some for a post jam version.
The idea of a maze or system of underwater caves is interesting. There could be a mechanic where you have to dive through underwater tunnels that are too tight for the submarine to navigate, but you have to memorize the map with your radar before entering them so you don't get lost.