Take a look at;

http://www.hookahdivegear.com/catalog.htm

Also there is a DIY artical for a syston.

http://www.yandina.com/hints.htm

Mike
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I'd like to clean the bottom of my boat, while it's
in the water. Is there a fairly easy and economical
way of breathing while a few feet below the surface?
A snorkle won't work because I'll be going under
a houseboat, but am wondering if a hose could
be made to work, or maybe a larger piece of tubing
with a hose attached so it's small enough to be held
in your mouth. Or something...?