To be honest, my favorite dives in Cozumel are usually the shallower ones; the light is better, there's typically more marine life. One exception is Colombia deep; and that's usually less than 110 ft. Fantastic algae fronds and rock formations on that one. But, some of the nicer shallow reefs, like yucab and cedral pass, are really spectacular. I think the advantage of the more southerly locations is fewer divers, especially in the morning. I'd look for a small dive op that caters to more advanced divers (if you can find one) and specify that you want to avoid the crowds. I've had good luck with scubashack, aka Roberta's Eco-dive cozumel. They're getting bigger, though, they just bought blue bubble divers, and with that came a couple of more boats. Hopefully, they'll be able to handle the inevitable increase in cruise ship/novice divers on the larger boat and save at least one of the small boats for people in your situation. There are a surprising number of single, relatively advanced divers on cozumel, and the better, smaller dive ops should be able to accomodate you. I would advise being as up-front as possible about your preferences and make sure they give you a straight answer.