hey, what's up!
back in the day when this collab just started we had an idea to include underwater tunnel - that's what that brown boxy thing is (with the glass round ceiling).
and behind / below that tunnel isn't a cliff - that's actually body of shipwreck gawrone asked for. so it was meant to look roughly like this:

with texture on the shipwreck i tried to mimic it to be covered with marine life:

but i understand that at this stage it isn't much obvious what it is.

you're honestly in difficult spot with the tile 95 as on top of those two things there is the problem that the underground wasn't meant to be under water, which was happily ignored by others :]]

all i can think of is to finish the shipwreck, turn the tunnel down and make a huge wall with air lock to separate water on the left from the underground complex on the right.
but maybe you have better ideas what to do there...