1. Regarding maze rooms, in no way are you expected to farm them. Things that are useful for getting to parts of the world, like acid gills, are typically found in stash rooms instead of through a maze room, partly for that very reason. Sorry for the confusion. Also, the music track "for maze rooms" is no such thing. There are various indoors music tracks that vary based on the region type you are in, and so the tune was just based around that.
2. Regarding the underwater stuff, we don't even have proper enemies in there yet for that. We're like 10% done with what we need to have that really work well, to be sure.