Hotel Cozumel is optional AI. We opted not to eat there. Maybe that's part of the reason why we found it pretty impersonal and didn't meet a soul--that and it's kind of huge. You've possibly read that the closer-to-town southern hotels tend to have man-made beaches. To its credit, Hotel Cozumel's is bigger than most, and their pool is billed as the island's largest. And they have organized activities (bingo, dance lessons, etc.), if you go in for that sort of thing. Cruise ship passengers visit frequently--I think they buy day passes. I'm pretty sure Hotel Coz wouldn't be anywhere near my top choice if I were traveling alone, but it's an okay place to sleep, and the location is good, other than the rooms not being on the water. And it's fairly cheap.
And for the record, I like the boat rides too.
You said Blue Angel was looking okay to you, but they didn't have rooms for your dates. I know they frequently put people into the Villablanca for overflow (if BA does the booking, they might give you breakfast at BA--not absolutely sure). Some of the (superior) rooms at the VB are pretty nice, and it's close enough that if you're diving with BA, you'd probably be comfortable hanging out with any new dive friends at the restaurant. And there are a couple of congenial bar/restaurants right by the VB as well. The hotel itself doesn't quite have the intimate vibe that the BA has, or the unobstructed views, and you might yet find options you like better, but it's not a terrible way to go.
If you're willing to forgo a more social hotel, a good waterfront balcony at Casa Mexicana, Vista del Mar or similar place gives you lots of eye candy in lieu of conversation. Dive pier across the street, but not as many operators pick up from there--not that you'd likely be complaining.
If you go too far south for a hotel, it is pretty much resort after resort, punctuated by beach clubs. Couple of independent bar/restaurants, but most people down there are doing AIs.
