Île Plate, about 11 km north of Cap Malheureux, is the largest of the offshore islets and the only one that catamarans regularly land on. It is a long, low limestone platform with two beaches, a 19th-century French lighthouse, and the abandoned ruins of a quarantine station that once held cholera victims from arriving immigrant ships.
The reef on the leeward side offers some of the best snorkelling on a standard day trip — shallow, clear, and full of parrotfish and butterflyfish. Bring water and shade; there is no infrastructure on the island beyond a few picnic tables. Catamaran operators in Grand Baie sail here daily in season.