You don't often see a GL who can't go just anywhere he likes. Usually they're air breathing humanoids, but what if one of them was a sea creature who always had to be underwater? He could go anywhere of course, because of his ring. He could create a fine field around himself filled with water. But should he got knocked out in battle, there goes his protective ring of water... and source of air/life. I think it would take a lot to get these GL's out of their natural habitat.