Grand idea, but I don't think it would work. As Sensiride said, THC isn't water soluble ... But get a Beta (Siamese Fighting Fish) for like $5, and they actually breathe air (they swim to the surface and take a gulp of air). It should get him high, just don't clear the chamber until after he takes a hit too ;)
I'll try it sometime soonish, and letcha know how it goes.