If you like diving you need to visit the Cancun underwater museum.
Cancun Underwater Museum is a series of sculptures by Jason deCaires Taylor placed underwater off the coast of Isla de Mujeres and Cancún, Mexico. The project began in November 2009 with placement of a hundred statues in shallow waters of the Cancún National Marine Park, which had been previously damaged by storms.
The sculptures are created with pH-neutral marine concrete and are based on members of the local community. The artist planned the sculptures as artificial reefs with fire coral planted in the initial sculptures.
Source: Wikipedia