So now we already made ot to a WIP-thread, great!
So what du you mean by exploration? will there "only" be the underwater landscape to enjoy, or are you planning to add some more things like a little loot, maybe caverns, an underwater playerhouse with a bulleye as window, new fishes?
don't get me wrong, swimming around there would be great on it's own, but maybe some things like the listed would force the players a little more to acually dive/explore there and search for hidden things...if you want to keep it strictly to the lore, then juast forget about the stuff i just wrote
or: there are some guys who are "inventing" some underwater-dwemer stuff? that'll be cool