Yup- I was thinking the same thing. On practically every deserted stretch of beach in the Caribbean there's an accumulation of discarded plastic bottles. They've all passed thru someone's hands before they ended up there. Since that realization, I've always packed my own refillable water bottle -- to use in the room and on the dive boat. It may not be much, but at least it's a small help ...and my kids are watching.
That is excellent!!!!! Just think what a difference it would make if only half the people who vacation in Cozumel every year did that! I also like to bring containers of powdered drink mixes like Propel, lemonade, iced teas, so we aren't buying those bottled items too.
I have put this down sooooo many times on suggestion cards (and emails you get after a stay) - Please provide a good sized (18-32 oz) reusable plastic mug and a decent quality reusable shopping/tote bag to each of your guests at check-in. They are very reasonably priced when ordered in large quantities, and imprinted with your name, logo, web site and phone number, they will also serve as advertising for you when your guests are out and about using them, and when they take them home.
For a total of about $3 pp, just think of how much less plastic will end up on the side of the road and in the ocean!