I think that if I would go back to Cozumel being there 3 times.
First wide angle lens ideal Tokin 10 -17 mm , do not have one so ! have taken my Sigma 10 -20 mm. Wide angle a must.
But on the other hand a lens in the 17 - 70 mm or like my all go lens the Sigma 28 - 80 is another one to have in mind. These would allow you to capture reef scenes, fish and pseudo macros.
Lastly a macro lens for the Reef like Paraiso Shallow sea horses , Blennies and small critters.
Good Shooting and Luck