Beginning life some 450-500 million years ago, the Earth's coral reefs are now the largest ecosystem upon the planet. They sustain and support over 1 million species worldwide and one coral reef alone may harbor some 3000 species. The major Indo-Pacific ocean currents cross the seas that surround Sabah's sandy shores making them amongst the most bio-diverse marine environments in the world. Within a single dive around Pulau Layang Layang divers may observe many of the 150 species of butterfly fish. Used by marine biologists as indicators of coral reef health, the greater the number and species diversity of butterfly fish reflects the abundance and diversity of corals. Pulau Layang Layang's pristine coral reef not only plays landlord to countless butterfly fish but also other reef dwellers such as, angelfish, snappers, wrasse, sweet lips, parrotfish as well as the larger pelagic; barracuda, manta, schools of hammerhead sharks, dolphins and whales. Pulau Sipadan is famous for its vast numbers of Green and Hawksbill turtles which feed and breed within its waters before the females climb ashore to lay their eggs above the white sandy beaches.

Diving on Sipadan's coral reefs, one can witness the incredible phenomenon of thousands of schooling chevron barracuda and., big-eye  'Jacks'. Floating inside such a tornado of fish is a truly breath-taking experience that's very hard to beat.

Islands in Sabah is also becoming a world famous location for 'muck diving' - the term used by divers to describe the search for the rare and exotic small marine animals. rare and newly identified gobies can be found living in the corals, sand, mud and mangroves of Sabah along with the little understood and rarely seen mimic octopus, neon patterned blue-ringed octopus, delicate flamboyant cuttlefish, psychedelic mandarin fish and ghost pipefish. Sabah's dive guides are specifically trained to find such rarities and can show divers several of these oddities on a single dive. Many new islands and reefs are being explored around the coast of Sabah and with this exploration come the discovery of new dive sites and rarely seen marine creatures.

Around north Sabah and the more recent discovered Mantanani Resort rare sightings of dugongs have been recorded. With the yearly occurrence of whale sharks along the west coast during the months of December to February, Sabah really has some spectacular marine creatures to be discovered by visiting divers.

Sabah and its surrounding waters have been recognized as a marine turtle sanctuary since the opening of the Turtle Island Parks on its east coast. Managed by Sabah Parks, the beaches welcome nesting green and hawksbill turtles every night all year round. Similarly, the Wildlife Department monitors and protects nesting green and hawksbill turtles that visit Pulau Sipadan's shores. On nearby Pulau Mabul, the Fisheries Department together with Sipadan Mabul had sunk hundreds of concrete pipes to form small artificial patch reefs surrounding a small wooden shipwreck. A fish poaching vessel was also sunk off the island of Pulau Lankayan and already hosts a myriad of creatures from the smallest ghost pipefish to the giant stingrays and schooling barracuda.

Sipadan Water Village on Pulau Mabul, is also actively engaged in coral reef research. Dive masters and instructors are encouraged to study both the fish and coral life in detail in collaboration with a Japanese Natural History Museum. Each year, in June, the dive center's management and outside guest speakers run a specialized Marine Day and provide hands on lectures to guests sharing their studies' and encourage them to take part in their coral relocation and growth studies so that divers may learn more about the coral reef environment.