July is chock full of Puerto Rican holidays, so be prepared for significant crowds. Great snorkeling beaches on the leeward side of Culebra, including Carlos Rosario (aka Impact), Tamarindo, Melones and Punta Soldado. Signature beach Flamenco will be packed, so you may wish to travel to Zoni, where the view to the VIs is eye popping, unless Sahara dust is in the atmosphere.

I can't do the beaches justice in a week, so choose according to your preferences for a three day visit.