Great game! You put a some efforts into this I can tell. I played with headphones and highly recommend it.
The scenery is great and the audio engulf you into the underwater, you feel submerged. Combat was simple but effective.
You can end up on same tile as the enemy, not sure if this has to be addressed.
Holding forward to move is a thing which I really appreciate, but the movement could be faster. Some games like this you don't want to move to fast but then queuing up next move so it feels more responsive is a suggestion that I think would improve significantly.
The lost souls audio pick up was a neat thing which I think you implemented well. Story wise you did a really good job! Well Done!