Terumbu Layang Layang, 'Swallow Reef' on Admiralty charts, is an isolated submerged coral atoll in the South China Sea, 306km northwest of Sabah's capital Kota Kinabalu. It has a man-made island covering 6 hectares situated on the eastern end of the atoll.
It is uncertain, whether this is an oceanic island formed by coral growth capping an extinct undersea volcano or a sunken mountain. Specialists believe that thirteen coral reefs linked up to form the 7.3km long, 2.2km wide atoll. The 20m deep enclosed lagoon, with its fixed mooring buoys, is the only safe anchorage in this remote region.
The reefs are pristine and the visibility excellent. Steep walls over extremely deep water provide spectacular diving. Resident shoals of barracuda and caranx are becoming accustomed to divers, while dolphins occasionally interact with them. Hawksbill and Green turtles are frequently seen resting on the reefs. Healthy corals are plentiful, sea fans exceeding three metres across filter planktonic food from the passing currents and yellow, red and purple soft tree corals grow to two
metres or more across in deeper water.
Set in a vast open sea, the reef attracts pelagic species, barracuda and Bigeye Trevally occur in large shoals and Oceanic Triggerfish arrive to nest in the warmer months. The northeast corner is a unique location where encounters with large shoals of Hammerhead Sharks are common when the water is colder during the months of April and May. On numerous occasions hundreds of these shy creatures are seen but they always keep just a little too far away for cameras to record clearly. One is only likely to have close encounters when small groups of them approach the reef while stalking Bigeye Trevally into shallow water.
On land, with more sand permanently exposed than on other islands in this large area, the atoll is a favoured nesting side for many species of migratory sea birds. There is a seasonal increase in numbers during the nesting months from February to October, when Brown Boobies, the commonest of the tropical gannets, with Noddies and Great Crested-Terns compete for space in raucous colonies. When alarmed the adults take off leaving well camouflaged eggs or chicks strewn everywhere. Tireless fliers, terns are often called 'Sea Swallows' because of their forked tails, hence the reef's name 'Swallow Reef'.
