I meant that underwater environments seem limiting to those who haven't played in them. I think when you consider that your characters can (in effect) fly and travel at high speeds through currents, there are plenty of options.
I've always liked the idea of a deep-sea D&D game as well (although, sadly, I've never seen the Abyss). There are some great campaign ideas you could run with. A long hunt across the Abyssal plain, or a mass migration. Many of the deep-sea ecosystems are fragile, especially hydrothermal vents, so imagine what happens when an entire community based around black smokers suddenly collapses when the vents stop spewing. The players would have to lead their people (their blind, albino crab-people) across the plains from whale-carcass to whale-carcass, searching for the new promised land.
I've always liked the idea of a deep-sea D&D game as well (although, sadly, I've never seen the Abyss). There are some great campaign ideas you could run with. A long hunt across the Abyssal plain, or a mass migration. Many of the deep-sea ecosystems are fragile, especially hydrothermal vents, so imagine what happens when an entire community based around black smokers suddenly collapses when the vents stop spewing. The players would have to lead their people (their blind, albino crab-people) across the plains from whale-carcass to whale-carcass, searching for the new promised land.