I'm thinking more or a Control Power than Elemental/Energy... more of clasic waterbending that requires a ready source of water than manipulating watervapor in the air to generate their own watersource. It may not be as flashy as being able to create water sponateously like the aliens from the Dr. Who episode "The Water of Mars", but I think that fitst better for the character I am going for.
I am wondering though why the deigners overlooked this often possessed (though also often overlooked) power.