How about doing a dry-dock instead of a moon-pool? i.e. the room has a door on the top, not on the bottom, and when the sub connects, it closes up and pumps out all the water.
I exclusively use Rabbit Rays, because out of some glitch, they don't get ground up, and so work infinitely for some reason. Also I literally have a tank so full of them that I think there are move rays there than water.
I choose the mountains, purely because the first time I was there, I was NOT aware there were Reapers there. And I've not seen or heard a single Reaper while I was there. Basically, I was amazed at just how LUCKY I was when I was there, and that gav…