Tourmaline Reef (Spanish: Arrecife de Tourmaline) is a shelf-edge reef located in the Mona Passage off Mayagüez Bay in western Puerto Rico. The reef is one of the best-preserved reefs of its type in Puerto Rico as it is found far away enough from the coast and was selected as one of the first coral reef protection zones under the Puerto Rico Coastal Zone Management Program (Programa de Manejo de la Zona Costanera de Puerto Rico). Tourmaline Reef is located close to Punta Guanajibo, at 7.5 nautical miles from Mayagüez, at depths of up to 10 meters under the ocean surface bordering in waters of moderate to high visibility due to minimal terrigenous or sedimentary deposits.[1]