I went scuba diving nearly every weekend that I was in San Juan. My first weekend I went out to the Eastern coast and was somewhat disappointed in the visibility and fish (or lack there of). At the end of the dive, I ask the divemaster for recommendations on dives around PR. His immediate response was "go to Desecheo." Furthermore, he even highly recommended Taino Divers in Rincón. So, that's where I went and love it.
Desecheo Island is a small, uninhabited island about 12 miles off the Western coast of PR in the Mona Passage. The island's terrain is quite rugged, rising some 600 feet out of the sea. This same profile is carried below the water's surface, sinking some 100 feet to the ocean floor. So, you can literally start a wall dive from the surface. Several pinnacles near the island also rise dramatically to the surface making for some very interesting underwater rock formations. Finally, the best thing, all three weekends that I dove Desecheo, there was no other dive boat present;so, the place is all but deserted.
Equipment: Taino Divers will have everything you need. What's more, the dude that runs the dive operation is very cool and laid back. And their dive boat makes the 12 mile trip from Rincón to Desecheo Island in no time. This was truly one my favorite dive sites/experiences.