The San Bernardo archipelago is a coral group of about ten small islands lying offshore from Rincón, part of the same national park system as the better-known Rosario islands near Cartagena. The closer islands — Isla Tintipán and Isla Múcura — can be visited as a day trip from Rincón by panga boat, with snorkelling stops on the reefs along the way.
At night, the lagoons between Tintipán and the mangroves glow with bioluminescent plankton — swimming through it on a moonless night is one of the best things you can do anywhere on the Colombian Caribbean. Many Rincón hostels offer a night tour. Bring a hat, sunblock, and small bills; nothing on the islands accepts cards.