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Similan Island

This group of rocks and islands, 34 miles west of Thap Lamu and 50 miles northwest of Patong, was declared a marine National Park in 1982. Consequently it remains today largely undeveloped. The name is derived from the Malay `sembilan`, meaning `nine`, and refers to the nine main islands in the group. The islands are commonly named from 1 to 9, running south to north; Koh Similan itself, for example, is #8. Each also has a name, as we show on the charts, though even local fishermen might not recognise them. There are National Park ranger stations on islands #4 and #8.

The waters surrounding the Similans are teeming with tropical fish, colourful coral, and offer exceptional underwater visibility at most times of the year. The diving is certainly the best in Thailand, and compares favourably with some of the best in the world. The Similans, along with the islands and rocks to the north, are now a recognised feature on the world diving map, and are particularly noted for the regularity with which divers meet whale sharks and mantas.

Similan Island

The submarine topography is especially interesting, due in part to huge granite boulders, which not only litter the shorelines, but also lie in jumbled heaps beneath the waves to a depth of 35 metres plus. On the surface the boulders, together with the lush forest and silica white sand beaches, provide a peaceful refuge from the crowded beaches of Phuket.

During the high season from November to April one can expect to find up to 50 dive boats seeking shelter in the bay at Koh Similan, and the mooring buoys are very difficult to obtain. The continental drop-off is only a few kilometres west of the Similans. This attracts the occasional game fishing boat to venture out from Phuket, invariably seeking the legendary huge Black Marlin reputed to pass there.

The entire group is patrolled by National Park launches. Officers collect 200 baht per vessel and another 500 baht for each passenger per day. Each scuba diver is charged an additional 400 baht per day.

All commercial operators are required to purchase vouchers in advance for vessels and passengers, then report to National Park HQ at Koh Miang upon arrival to have them verified. This is currently not applied to independent yachts, but may change in the future as Thailand becomes more eco-conscious of this tremendous tourist asset in the Andaman Sea. The rangers also check to ensure that no one is trolling, bottom fishing or spear fishing within a five-mile limit of the islands. Hefty fines are levied for offenders.

Basic accommodation is available at the HQ. For reservations, call the Phang Nga Office (+66 76 959045 or +66 76 421365).

Cruising to and among the Similans is not recommended during the southwest monsoon season, due to heavy swells and squalls together with a scarcity of protected overnight anchorages.

The lighthouse on the main Similan Island is reliable and clearly visible for up to 15 miles when making an overnight passage to the islands.

Koh Bon

Approximately 15 miles northeast of Koh Similan is Koh Bon. Surrounded by very deep water, anchoring is not possible.

On the southwest side orange National Parks moorings are available for shelter from the strong winds. There is a blow-hole cave that runs right through the north part of the island. Koh Bon has become a famous dive site because mantas are almost guaranteed here in the high season. If you?re lucky enough to secure a mooring, the etiquette is to allow another vessel to tie off your stern.

Koh Similan
  • A


61 miles from Patong Bay

KOH SIMILAN. 8° 39.921N, 97° 38.730E

The bay on the northwest side of Koh Similan (Island #8) is the best protected overnight stop in the group. Inside the bay, on the 8-12 metres sand and coral outcrop shelf, the government has installed moorings for general use.

Other moorings laid by dive shop operators can be used if vacant. However, dive boats often return in the late afternoon to use the moorings. If all moorings are taken, anchorage is only possible on the outer edge of the bay in 15-30 metres.

The bay has a beautiful white sand beach and interesting forest walks. The climb to the top of the distinctive rock formation called Donald Duck, overlooking the north end of the beach, is worthwhile. There is easy access from the beach or the boat to excellent snorkelling and diving around the rocks on the north side of the bay.

There is a National Parks campsite, bungalows and a small restaurant ashore on the beach.

Dive operators invariably refill their tanks in the late afternoon or early evening. If you want to avoid the noise of the compressors, anchor away from this crowd – that probably means you’ll have to move deeper.

In the high season there are numerous ferries and speedboats that arrive daily before midday and depart for Phuket during the mid-afternoon. This is helpful for crew changes or pick-ups or returning to Phuket in the case of emergency.

Amazingly clear water in the Similans – Photo by Paul Johnson
Koh Miang
  • B


56 miles from Patong Bay

KOH MIANG NATIONAL PARK HQ. 8°34.365N, 97°38.209E

Anchorage is in 12 metres, as the sandy bottom starts to fall away to deeper water. Completely open as it is to the northeast, it is not a good overnight anchorage when the monsoon is strong or unpredictable.

Beautiful white sand backs fringing coral gardens, which extend some 200 metres off the beach. In the trees behind, the national park headquarters for the Similan Islands offers some basic bungalows, tent camping grounds and a small restaurant.

There is great snorkelling and shallow diving on both sides of the bay. Ashore you’ll find easy trails for forest walks. The trees that overhang the beach here, including the ‘poison fish tree’ (named for the effect its seeds have on fish when ground up), are attractive and noteworthy.

  • C


56 miles from Patong Bay

KOH MIANG EAST. 8° 34.163N, 97° 38.554E

A better anchorage, one sheltered from both the northeast and the southwest is between Koh Miang and the small islets to the east in about 10-15 metres on a sandy bottom. Though a strong current runs through the channel, the holding is good.

Closer to the beach on Koh Miang, anchorage can be found in 8-10 metres on a sandy bottom.

Access either to the park headquarters beach or to a smaller beach opposite is easy by dinghy. There is a trail from the smaller beach to the park headquarters.

The snorkelling and diving is excellent around the small islet and among the coral heads, which appear indigo against the intense blue-green of the deep clear water.

The Similans, north to south (Island #9 to #1) - Photo by Image courtesy of Lee Marine International Marine Brokerage. Photographer: Jim Poulsen
The Similans, north to south (Island #9 to #1) – Photo by Image courtesy of Lee Marine International Marine Brokerage. Photographer: Jim Poulsen

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While every effort has been made to ensure that the information contained in this book is accurate, the charts of anchorages are based on personal experience and satellite imagery and are intended as a guide only. They should not be used for navigation. Please refer to Official Hydrographic Charts of the respective countries.

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