THE emerald waters that surround the Malaysian peninsula and its islands offer some of the best sites in the world for scuba diving. Underwater sanctuaries support a prolific ecosystem of coral reefs, algal beds, sea turtles, giant clams and an equally impressive variety of brightly coloured tropical fish. The coral reefs fringing the islands are close to shore, making them easily accessible by boat from most fishing ports on the peninsula, which serve as the main ''jump-off'', points to the islands. The established sites are just the tip of the atoll, with many extraordinary diving areas remaining unexplored. Facilities compare favourably with world standards and diving operators are normally well-qualified and experienced. Malaysia has a good transport network which ensures access to even the remotest reefs and resorts are normally well developed, but unobtrusive. The best time to go scuba diving is between March and October as out of season choices are more limited. The winter monsoon reduces visibility and makes surface conditions difficult. The most popular destinations off the peninsula are Tioman island in the Pahang Marine Park and Payar island off the Kedah coast. Divers who have visited Tioman compare it to Australia's Great Barrier Reef. A rugged marine environment of pinnacles, caves and canyons, it provides the perfect habitat for a profusion of undersea life. Several species of shark roam the area and multi-coloured fan corals and anemones attract large numbers of tropical fish and pelagics. Turtles are also sighted regularly. Most dives are safe and relatively shallow. The popular spots are the reefs along Salang beach and near Tulai island. At the northern end of the Malacca Straits lies a cluster of islands gazetted as a marine park since 1985. Foremost among these is Prayar island, noted for its sandy bays and colourful underwater havens. Fringing the southern tip of the island is a beautiful coral garden reputed to have the largest number of coral species in the country. The waters are also home to a prolific variety of sea squirts, sea slugs, hermit crabs and feather star fish. Less accessible is the island of Sipidan, about 30 kilometres off the southern coast of Sabah. It is a small island once described by undersea adventurer Jacques Cousteau as ''an untouched piece of art''. The island is surrounded by coral, which protrudes above the water at low tide. At the edge of the reef, the walls drop straight into the depths of the ocean. The reef attracts white tip, black tip and a few leopard and whale sharks, as well as large tuna, barracuda and mantas. This area is only for very experienced scuba divers and the diving is best off the eastern edge of the island from the jetty at Barracuda Point. Also off the coast of Sabah, but suitable for less advanced divers, is the Tunku Abdul Rahman Park. Off the west coast, about 20 minutes by boat from Kota Kinabalu, are the islands of Gaya, Sulug, Manukan, Mamutik and Sapi. The pounding from the open sea and the ravages of the monsoon have taken their toll on the northern and western shores of these islands, giving the undersea landscape different characteristics than areas closer to peninsula Malaysia. Diving in the park is rated fair to good. Other popular areas include the islands off the Terengganu coastline, where the sunken cliffs of Tenggol island, near Dungun, provide a spectacular place to explore; the area off the coast from Mersing, including the islands of Sibu, Mentinggi, Besar and Rawa; Tiga Park island, 48 kilometres south of the Tunku Abdul Rahman Park; and the Turtle Islands Park, 40 kilometres from the northeastern town of Sandakan, in Sabah, where the Green and Hawksbill turtles are the main attraction.