The game really looks nice. This music is super good, and the gameplay is quite nicely designed too! Going down and down into the abyss really builds up the anxiety, the map is also increasingly harder the further you go, which, combined it's really matches the deep sea theme you are going for. Nicely done!
For some nitpicks I think the game is a bit slow at the moment when it comes to game progression. It felt like each upgrade took a really long time to do, and pairing with the fact that it's perma-death makes re-running very frustrating. A strange thing I noticed about your game is that, for some reason, the whole screen (even the itch page) blinks randomly once you travel downwards. Not sure if that's intended but it worries me if it's breaking the browser.
Anyway, this is a really nice entry. Well done!