Saint Martin's Island is the only open-sea island of Bangladesh, a sliver of sandstone eight kilometres long under coconut palms in the Bay of Bengal off the tip of Cox's Bazar, whose tidal boulders carry the only living corals in the country, and it is reached by ferry from Teknaf in the winter season, now closed to visitors for most of the year to save it from the crowds. The island's boats are narrow, high-prowed and painted in bands of red, yellow and blue, and they come straight up onto the sand at dawn rather than tying to any pier; twice a day the sea pulls back and uncovers a wide plain of dark rounded sandstone boulders pooled with trapped water, walked out onto at low tide, and in a few shallow clear-water spots off the southern and western shore the boulders below carry living coral, worked over by small reef fish and snorkelled from the beach, though the belief that the island has a coral reef runs so deep that marine scientists have had to publish corrections to papers that measured one. The walk to Chhera Dwip, the tail of the island and the end of Bangladesh, runs on a clock, since the tail joins the island only at low water and the rising tide closes the sand behind as fast as in front.
Saint Martin's was an overlooked fishing island until a novel of 1990 sent a generation of Bengali readers looking for it, and the visitors who followed built hotels on an island with almost no fresh water of its own, whose wells are turning salty, so the government limited the numbers and closed the island outside the winter. Olive ridley turtles crawl up the dark beaches after sunset to lay through the winter, and the hatchlings emerge into February and March after the island has closed. Saint Martin's is the one island Bangladesh has in the open sea, and it is being rested.