Coin de Mire rises 162 metres from the sea eight kilometres off the northern coast, a basalt wedge visible from every beach in Grand Baie. The uninhabited island marks the edge of the shallow Mauritian plateau, where the reef flattens into a submerged shelf and the Indian Ocean drops to abyssal depth. For two centuries it served as a navigation landmark for East India Company convoys rounding the cape; today it anchors the northern catamaran circuit that departs daily from the public beach. The northern islands lie within a marine park gazetted in 1997, extending from Bain Boeuf to the tip of Cap Malheureux. Île Plate and Île Gabriel sit five kilometres offshore, low coral atolls fringed by white sand and ringed by shallow lagoons that remain below four metres at high tide. The seabed between the islands is a mosaic of seagrass meadows and coral heads, habitat for parrotfish, sergeant majors, and green turtles that migrate seasonally from nesting beaches in the Chagos Archipelago. Snorkeling conditions peak between May and November when southeast trades flatten the swell and visibility extends beyond twenty metres. Catamaran operators launched the Grand Baie to northern islands route in the early 1990s, replacing the wooden pirogues that had carried fishermen to the banks since the nineteenth century. Modern twin-hulled vessels draw less than a metre, allowing them to anchor inside the reef line and deploy swimming platforms directly over the coral. The tour pattern is fixed by marine park regulation: departure by nine, snorkeling off Coin de Mire's eastern flank, midday anchorage at Gabriel Island for barbecue service on the foredeck, return via Île Plate's lagoon. Operators provide mask and fin sets, safety briefings in French and English, and an open bar that runs the duration of the eight-hour crossing. The route covers approximately thirty-five nautical miles and returns to Grand Baie by late afternoon, timed to the prevailing wind that swings southeast after two. The northern boat tour remains the most-booked marine excursion in Mauritius, with sixteen licensed operators running a combined fleet of forty-two catamarans. Peak season spans June through September, when advance reservation is necessary. Weather cancellations are rare; the northern coast is sheltered by the central plateau and the reef breaks the ocean swell before it reaches the anchorage.