I'm interested in doing some underwater photos in a pool. I'd like to use 120 film. Obviously, the depths are not great so I don't need super gear. Is there a cheap and easy way to do this, or only expensive, new, and difficult?

I have Pentax 67 and Mamiya 7, but if the underwater housing is cheap enough, I could buy a camera to match. Otherwise, it looks like a Nikonos might be my best bet.