I found this a few days ago - it's pretty good. If you're new to hookah's, or just want to brush up on diving physics, you might want to check out the Air Line web site: http://www.airlinebyjsink.com/training.html. I'm thinking of going with their 12V unit but havern't yet. To find it: from their home page scroll down to the blue bar on the left, "Technical". Click "Training". At the top is a blue/purple line "Hookah Home Study Course, On-Line, Free
" (something like that). It's about 140 pages, lots of diagrams, not much type. Looks like good stuff to me. Wha' du ya think? (PS: I don't work for or know anybody with the company) 
Flyfuy
" (something like that). It's about 140 pages, lots of diagrams, not much type. Looks like good stuff to me. Wha' du ya think? (PS: I don't work for or know anybody with the company) Flyfuy