There are a lot of cruises from Tampa to Mexico. Carnival Cruise Line, Holland America Line, Norwegian Cruise Line and Royal Caribbean all offer them. Destinations in Mexico include Cozumel and Costa Maya.
Costa Maya (Mexico) was developed specifically as a cruise port. It is like a resort with pools, restaurants, and shops. There are white sand beaches with shallow surf at the village of Mahahual. A big attraction is the close access to Mayan ruins in the Yucatan peninsula like Chacchoben.
Cozumel (Mexico) is the big name stop on Mexico cruises. It's an island with a large underwater reef. Go snorkeling or diving to see tropical fish, turtles and other sea life. Interact with dolphins at Chankanaab National Marine Park. Take an excursion to the nearby ancient Mayan city of Tulum.