Unfortunately the cruise ships feed the economy of the island. Imagine "Sunday in Cozumel" seven days a week. Many restaurants will be closed. Taxis are scarce. Shops, including pharmacies, that sell the items that everyone, including locals and divers, needs and wants will be on restricted access. Mega and Chedraui (sp?) will cut back because no one will have any money. The cruise ships and their passengers drop tons of money in Cozumel, like it or not, which makes it easier and cheaper and nicer for all of us divers.
I think it's irresponsible to refer to people who are just trying to have fun in a different way than us divers as @BoundForElsewhere has. I agree that the cruise ships are contributing more to the declining health of the reefs than the divers, and reduced cruise activity may be good for Cozumel, but let's not throw out the baby with the bathwater.
Cheers - M²
I did not mean to disparage the cruisers. They are just regular people having fun in the best way they know. It was more a statement on what happens when you put too many people together on a floating petrie dish with very limited resources to manage any sort of outbreak, build up of waste, etc.