Layang Layang Island

 http://www.layanglayang.com/

The little land mass supports a luxurious 90-room dive resort, a Malaysian Naval base and a nesting colony for several sea-faring migratory birds.

The reef topography is essentially made up of a rich growth of hard corals; some so shallow that they break the sea surface during low tides, but most begin at depths of about 5m right down to the ocean floor.

Some of the marine animals observed around the 14 dive sites include black-tip sharks, hammerheads, jacks barracudas, bump-head parrotfish, lionfish, moray eels, turtles, nudibranches, gobies and the ghost pipe fish.

If you have ever wanted to see a school of huge hammerhead sharks, come in the months of April-June. Your chances are very good during this time.

Cow Island

http://www.abcsabah.com/islands-beaches/tunku-abdul-rahman-national-park/pulau-sapi/

Pulau Sapi has one of the nicest beaches in the Park its clean white sand and crystal clear water and coral reefs fringing the shoreline makes it ideal for swimming, snorkelling and diving.Day-use facilities include a jetty, picnic shelters, barbecue pits, tables, changing rooms and toilets. Pulau Sapi (Cow Island) has some of the nicest beaches in the Tunku Abdul Rahman National Park and pristine diving and snorkelling conditions.
The water is very clear and inhabited by colourful fish who peck in a surprising way at the feet and legs of unsuspecting visitors - they're just eating shreds of your dead skin... The island is also home to monkeys, not cows, and they're more than happy to steal your lunch if you give them a chance - out of your hands if need be. This is one of the quieter of the national park's five. People generally visit for the day and only a few people stay overnight - the accommodation is limited and the facilities pretty basic. But they do a tasty barbecue.