Just spent an amazing week in Cozumel and can't say enough good things about the crew at Dressel Diving there.
We did a Discovery Dive with them which was the standard lesson in the pool, then a 40min, 40ft dive on a reef, followed by a second "free$" dive on a different reef. We ended up trading in our pre-booked Snorkel day for another 2 dives. Very professional, safety conscious staff, descent equipment and apparently the marine reserve reef park is second only to Australia. I got to lay down on the sand a meter away from a 7ft Nurse shark on my 3rd ever dive.
The trip was booked through Westjet Vacations. Stayed at the Iberostar Cozumel which is not a 5 star kinda place so if your partner is high maintenance, you may want to go to Playa Del Carmen or Cancun on the mainland. It was however clean, descent food, and not a big ugly hotel. All rooms are in 4-8 suite huts. Friendly staff, plenty of booze and very few drunk college kids. The Dressel dive centre is right on the beech and they run 4 full boats, 4 times a day. The beech is nothing amazing, the pool is a chlorinated pool surrounded by fat leathery old people, and the restaurants are screened/open air so you can watch the flamingos and peacocks while you have breakfast.
$3000 all in for 2 for 8 days, plus about $600 for 8 dives. Flights were YYC-YYZ-Coz but you can fly direct to Cancun and take the bus and ferry. Great value in my books and will certainly be going back to do our open water.
I'm hooked on yet another very expensive hobby!
I'll put up some pictures once everything is downloaded. I'll be spending a couple evenings in Lightroom.