Southeast of Ponce off Puerto Rico, the snorkeling at Coffin Island (aka Isla Caja de Muertos) is considered one of the best spots in Puerto Rico. It is popular for shallow water with plentiful marine life. The water depth is up to 15 feet. There are a range of hard and soft coral reefs to explore filled with diverse marine life. Keep an eye out for dolphins.
To reach Puerto Rico by air, fly into Luis Munoz Marin International Airport (SJU). Isla Caja de Muerto is located about 5 miles off the coast. While there used to be a government-operated ferry, there is now only one private snorkeling charter tour boat. The entire islands is within the Caja de Muertos Island Nature Reserve.
Overall, Coffin Island is the 7th most popular snorkel dive spot of all 17 snorkeling dives in Puerto Rico.