I have friends in Cozumel who own a dive op and from what I understand, most of the "shore reefs" are off limits, so that will limit your hubby for shallow snorkeling, unless he plans to us a life vest, then you should book with Eagle Ray Divers and take their 3-reef snorkel package as it is AWESOME and a GREAT deal, too!! I've also done their resort dive package, 2 days and 2 tanks each day ($115 per day) .......AWESOME is all I can say!!! Enjoy and tell Chellie that Suzanne sent you.....
***edited to remove commercial reference***