If it's only 7' of water. Why not use a pool. I've done it in my pool testing equipment. I'm sure the agency that certified you would be more than happy to let you use their pool. I know I can walk into the store that I frequent out here, and as long as they aren't having a class, I can use it, anytime. But BobG is correct, it's not something you should do. New Years this year I went to CA to dive with someone. The night B4 he broke his little toe at work. We were even invited to tag along to Catalina with an Advanced open water class that Clarke was taking. My dive buddy suggested I could just go to Shaw's cove & dive alone. The water isn't deep & maybe I could hook up with some people while I was diving. But it's not how I was trained, and it's not something I would want to start doing. Everything is fine until that "1" time something goes wrong. I even use a redundant air supply, I still wont do it.