Looking for a "Do It Yourself" fishing day in either place.

It doesn't have to be a secluded beach but I would hope for at least a little casting room and a place for the wife to sit on the beach with a book while I try to catch a fish or three.

I have 9 hours in Belize and Cozumel each to play around with. I could rent a car but I don't really care to. I'll be arriving by cruise ship.

Is there anything I've described close by in either place??