Excursions in Cozumel

My son is going on a cruise which stops in Cozumel. I know in many destinations people recommend you book with a local operator rather than through the cruise ship company.
Are there any excursions that cater to the cruise ship crowd on Cozumel that anyone would recommend? Something like a snorkeling tour or a booze cruise that includes lunch and snorkeling? Also is it possible to book in advance?
Thanks

Playa Mia Beach Break fits the bill for a booze cruise, if that's his cup-o-tea. Pretty nice facilities, all inclusive. <img src="http://www.traveltalkonline.com/forums/images/graemlins/handshake.gif" alt="" />