Mayotte Lagoon & Double Barrier Reef

The lagoon of Mayotte, a French overseas department in the Comoros archipelago, is among the largest enclosed lagoons in the world, ringed by a barrier reef roughly 160 kilometres long. Part of the reef is a rare double barrier, with an outer and an inner line of coral, found on the eastern and southwestern sides of Grande-Terre. The lagoon encloses both Grande-Terre and Petite-Terre and shelters green and hawksbill turtles, dugongs, reef sharks, rays and hundreds of coral and fish species. The Mayotte Natural Marine Park, created in 2010, covers the surrounding waters. Most visitors experience the lagoon on a half-day or full-day boat excursion departing from Mamoudzou port or the Dzaoudzi pier on Petite-Terre. Typical itineraries combine snorkelling over coral gardens, a stop on a sandbank or islet, and a picnic on board or ashore. Experienced divers head for the passes cut through the reef, where currents bring in pelagic fish. Calm conditions and the clearest water occur between April and November, with boats usually leaving between 07:00 and 08:00 to beat the afternoon wind. Mornings give the flattest sea and the best light for underwater photography, while the late afternoon gives colourful views back toward the green hills of Grande-Terre. Crowds are never large by Mediterranean or Indian Ocean standards, though popular islets can host several boats at once at weekends and during French school holidays. Visitors are expected to follow marine park rules: no touching or standing on coral, no feeding fish, and a respectful distance from turtles and whales. Operators provide masks, fins and a guide, and prices are quoted per person, commonly between 50 and 120 euros depending on length and inclusions.