We will be traveling to Cancun next week and staying at the Moon Palace.
Having never been to Cancun we'd like some recomendations.
1) Dive operations: We've tried to contact Solo Buceo by email with no reply
after 4 days.  So looking for something else.

After an absence of several years, my wife and I want to return to scuba
diving.  We live in Waco, Texas and there is no decent diving within light
years of this place.
We have (in the distant past) been to Grand Cayman and Cozumel.  This time