Wow...I don't know how Rainbow buys all these recommendations; but they're bogus. You like diving on a boat with 25-35 divers? Fighting to get on and off? Being part of the underwater thundering herd? Yep, you'll see all of these with Rainbow's cattle boats; Same with Silent world and Conch. Look at the size of their boats; they pack them full as they can, and the end of May will be Memorial Day weekend. You'll be swamped with other divers on these company's boat. I PROMISE.
Here's who you want:
Quiescence Diving Services, World Class Diving in Key Largo, FL
Nitrox: Check.
Boat with less than 10 divers: Check. They ONLY run six divers per boat. NEVER any more. NEVER.
ON-SITE Gear storage: Check. They'll even haul it to/from the boat for you, in a nifty little cart.
Close to hotel: Check. It's the closest you can get to the center of the island; right next to the cut.
Wreck and reef: Check. They'll go to any site you want, and they have a list of sites that only they visit; that aren't moored sites.
There are so many benefits with them. They have secure parking; you'll never have to worry about what you leave in the car. Neutral AL80 tanks, without the big bouyancy swing common to AL80s. The best staff I've dealt with. They have guides for hire, but honestly, I don't think you'll want/need one. The reefs are shallow, and easy to navigate.
Now, I can't say that there'll be sharks. Nor can anyone; unless they're Neptune.