Blue Planet was sort of a poster child for why I wanted to start doing the One Hit Wonders. It is the pinnacle of “games bought because it sounded neat but no one ever actually wants to play.” And we played it, oh yes.
Many game lines will put out the “adventures with water” sourcebook. Shadowrun had Cyberpirates, oWoD had Blood-Dimmed Tides and Changing Breeds: Rokea. There were a few different things that came out over the years for D&D, I think.
Invariably they seem like a weird marketing choice, because they seem to be loathed by many people I talk to. And they are a little useless, because you really have to want to run an all-aquatic game. And not many people are really jazzed by an all aquatic game. Otherwise you can’t really make a character based off that sourcebook in many games. Being a cyberpirate in the Redmond Barrens is as useless as a fish on a bicycle.
It takes a special sort of dork to really want to play with these weird little settings. And I am that special sort of dork, my friends. I buy these books, put them next to my copy of Shadowbeat and practice my contrived slang from Shadowrun. (“Hoi! What the frag is up with all this hoopy drek, chummer?”)