Look for Heinrich C. Berann's works, they might help: Berann's panoramas
Now, concerning fantasy maps, off the top of my head I can only think in one story that has an arc in a underwater realm, the Cronache del Mondo Emerso by Licia Troisi, which, coincidentally, features a MC called Nihal. =P
The bad news: I don't think the editions I've read had maps and I can't find any map featuring water realm on google.
I know they weren't exactly maps, but I figured if you were creating your own map depicting the ocean floor, it might be a good idea to check out the surface features of the seafloor. Sorry