Blue Bay Marine Park is the most biodiverse and best-preserved marine ecosystem in Mauritius — a protected lagoon on the south-east coast declared a Ramsar Wetland of International Importance in 2008. The park covers 353 hectares of lagoon, seagrass beds, and coral reef, and holds over 50 species of hard and soft coral and 72 species of fish.

The reef here was one of the most affected by coral bleaching events in the late 1990s and has been the focus of intensive restoration work. Today it is in demonstrably better condition than the reef systems off the more heavily developed coasts, and the density and variety of coral visible even in shallow water is striking. Staghorn, brain, and table corals form complex structures that shelter reef fish, sea turtles, and the occasional octopus.

The simplest way to see the reef is by glass-bottom boat — operators based on the Blue Bay beach run 30-minute tours that pass directly over the best coral patches. No swimming is required, and the glass panels give a clear view even on choppy days. For snorkellers, the reef is accessible directly from the north end of the beach in about 2 metres of water; mask and fin hire is available from the beach operators.

Swimming is only permitted in designated areas — the park authorities enforce buoy lines to protect the most sensitive coral patches. Early morning visits (before 10am) offer the clearest water and fewest boats. The marine park rangers are helpful and informative. The beach at Blue Bay is also one of the nicest on the south-east coast — calm, sheltered, and lined with casuarina trees.