I've never understood why people choose quirky or obscure names for new retail businesses. Your ad budget is always going to be small, so the name of your store should tell people what it is you do. That way the sign on the store is a permanent ad that passersby will notice, and more importantly, understand immediately. Even if they aren't going into your store today, they will remember your store when the day comes that they want what you're selling.
For example, there's a store near me called Thursday Afternoon. Now what the heck do they sell in there? I sure can't tell from the name. Unless I go in there, or talk to someone who knows, or happen to see one of their ads, I'll never know. I think it's a bad name. Quirky names only work if they are backed up by a big advertising budget to build up public awareness.
I doubt that you will have lots of extra cash to spend on advertising. Most dive shops run on pretty thin margins. So if I were you, I would stay away from cute or quirky names, and go instead with something brutally obvious. How about "Big Mike's Dive Shop" or "(Your Town) Scuba Diving" or something along those lines? At least include Dive or Diving or Scuba in the name. Yes, it's boring. But boring works. Some guy who's never been diving in his life will be driving down the street and see the sign on your store, and remember it later when he suddenly decides to get certified. Your shop name just brought in a new customer. On the other hand, once your business reputation is established, your regular customers will keep coming back because they like your shop, not because they think the name is cool.