have you heard some of the samples you can get for that stuff. when i first suggested it, it was deep sea kinda stuff, beaches ect. you'd be surpirsed how far a whale noise will go for some atmospheric pads or dirt bass.
youre not gonna believe this thread http://www.muffwiggler.com/forum/viewtopic.php?t=64984 check it out, its absolutely packed with underwater music
anyways could be underwater concept is a little too abstract. i dont know. any other suggestions?