Three Islets

Three Islets (In Through the Out Door)

This large area consists of one small island and two large rocks, all of which rise well above the surface. Each could be considered a separate site; there is no way to see them all on a single dive, or even a full day of diving. All three islets are perfectly suited for multilevel profiles, with thriving marine life from the bottom to the surface. While the main island probably offers the best diving, both smaller islets are also worth exploring. The south islet features a submerged reef that nearly connects with the main island. Assuming you use currents to your advantage, it is normally an easy swim between the two. The north islet, on the other hand, is at least 100m from the main island and is best done as a separate dive.

Underwater, the combination of unusual topography and a tremendous variety of creatures makes this one of the best dive sites in the Mergui Archipelago. Nearly every square meter is riddled with crevices that provide shelter and holdfasts for an enormous volume of fish and invertebrate life. Typically, from the moment you leave the surface, you'll be surrounded by schools of silversides and fusiliers that frantically dash about trying to avoid the ravenous jacks and bonitos that harass them around the clock.

Before you look at the reef, it is worth doing a quick survey of the surrounding sandy seafloor. Although it may appear barren at first glance, a closer look will reveal a wealth of interesting creatures, including tube anemones, burrowing sea cucumbers and several unusually beautiful varieties of sea stars. While you are over the sand, look at the large brown sea anemones, as they frequently host eggshell shrimp, as well as sebae clownfish, a species seldom seen at other sites.

Moving over to the reef base, you will find sheer walls and dense colonies of orange cup corals around much of the perimeter. Elsewhere, the substrate steps down more gradually, creating an ideal base for rope sponges, whip corals a'hd huge stands of green tubastrea coral. Feather stars are especially prolific and often provide homes for various shrimp, squat lobsters and crinoid clingfish. These reefs are also blessed with son'1e very impressive red and yellow gorgonian fans, some of which grow in only 3m of water. Have a good look at these, since wellcamouflaged spindle cowries often hide amid the branches, along with hawkfish and occasional gorgonian crabs. Other noteworthy creatures found here include basket stars, jewel-box urchins, cuttlefish, squid and several species of cowries.

Fish life is also extremely diverse, with marbled rays, false and true stonefish, flatheads, Schultz's pipefish, badger clingfish, tigertail seahorses and several species of morays, in addition to most of the usual players. This is also one of the better places to see creatures like harlequin shrimp and harlequin ghost pipefish.
Aside from marine life, one of the most outstanding features of this area is a large canyon on the north end of the main island. While the rock walls making up the outer portions of this area are rather barren, there is a fair chance of encountering up to 12 or so semi-resident grey reef sharks. Generally inhabiting open coral reefs, these sharks are not usually known to hang around enclosed areas; it's a very unusual environment for this species. Typically these animals are not aggressive toward divers, but be careful not to corner them in the canyon; grey reef sharks have been known to vigorously defend their territory in such circumstances. The best approach here is to keep close to the rock wall on your right, and slow down as you enter the narrow parts of the canyon.

When you come to a rock archway, stop and have a good look around. If you are lucky, you may get to see several grey reefs patrolling this somewhat confined area, milling around in mid-water. If the sharks are present, just stay put on the bottom and enjoy watching them until they leave the area, which is usually within a minute or two. Once they leave, or if they are not around, continue into the canyon until you pass under the archway, then follow the wall to the right. Here you will see a tall, fairly wide opening to a tunnel that runs completely through the island and exits on the east side at about 15m. Plenty of natural light is available, but you may wish to bring a dive light to fully enjoy the colorful cup corals and yellow sponges that line the tunnel walls. Fish are plentiful here as well, with schools of small yellow snappers and copper sweepers hovering throughout the cavern.

Just below the main tunnel you will find a smaller cavern that runs roughly parallel to the main passage, with only enough room for two or three divers at a time. The site's second name, In Through the Out Door, is a clever reference to these twin tunnel entrances. Although this cavern also has an entrance at either end and is not especially dangerous, it can be very tricky if a big swell is running-be sure to check with your dive leader before entering. Be sure not to disturb the several huge (more than 3m long) tawny nurse sharks that sometimes rest within the crevices.

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