Try a large bookstore wth a comprehensive travel section, or search on line for books (Amazon, Alibris, etc.) that cover the many, many dive sites in P.R. from the east coast islands to the western and southern shorelines. There is plenty of excellent diving. Ponce, Culebra, the list is very long.
Most internet sites will be brief, and often more an attempt to sell than detailed objective info. You need a guidebook specializing in scuba in Puerto Rico. Even better, two current guidebooks. There are dozens of them.
Forget the internet as a source of good detailed information. Buy a book. It's the only way, really.