In order for a contract to be breached there needs to be... wait for it... a contract.
There wasn't a contract between the OP and the instructor, therefor there can be no "breach of contract" on the part of the instructor. The term "contract" has a very specific legal meaning. Accordingly, theere are certain, specific legal requirements for a contract to exist. Those criteria may vary slightly from state to state, but signing up for a scuba class doesn't meet those criteria in any state that know of. Pretty simple.
When I formally fire this guy, I'll be lucky to get a store credit for 10 bucks. Best I've got is a verbal contract with two separate opinions (and they will be completely different) as to what transpired. I don't know about anyone else, but when was the last time you tried to get any bank to do anything for an individual customer??? They are protecting their merchant accounts like a mother grizzly and her cubs. Last time we were defrauded by a on line company, my ex-bank, basically told me to go pound sand. . .nicely of course. I'm still going to try my credit union - but I'm not going to go against the most important rule of scuba diving (I have learned a couple things. . . .so not a total loss!)