I enjoyed this! Feels like a cross between Subnautica and Daggerfall. The level generation makes interesting enough labyrinths that you may find yourself lost in, but in a way that feels entirely on you. I personally wish the swimming had ascend/descend controls. My first play through I never found the second key chest, and I had to restart, but my second play through I got out.
It's worth getting to the end! Great work!