A small sugestion and fix.
I was thinking that to help fix the issue of us "falling" out of the base and walking on the sea floor (bug) the hatch and associated mechanics could be changed. By changing them I was thinking about making it so that if more than 50% of our body is dry (above water) we walk and if more than 50% is below water we swim. The hatch would be changed so it opens and the room it is attached to floods just like it does with the bulkhead door when one room is leaking and full of water. This will also make the game more realistic.