how about a site dedicated to girl-under-water fetish?
you could also incorporate the fear element, with girl looking very uncertain and scared before going in the water? "Do I really have to do this?", she asks...
And then elements of force, like the guy holding her underwater with his hands... Or girl-under-water initiation rituals, like a cadre of sorority girls who give the girl-under-water initiation to the new recruit... Or baptism gone naughty??? (hehehe...)
DrowningDolls.com ??
-or a younger-slant:
TeensUnderWater.com
I started this post as a joke and now I think the idea might have some merit...