The Similan Islands rank among top 10 dive sites in the world, but even for non-divers they are well worth a visit.Imagine yourself, a castaway on a tropical paradise, walking along a jungle path and discovering a stunning white sandy beach then swimming in its warm and transparent waters. This may sound like a cliché, but on the Similans it's everyday life...What is it that makes these islands so attractive? The Similans aren't as dramatically scenic as the limestone islands of Krabi or Phang Nga Bay, which many people have come to associate with the Andaman Sea. Instead, you find low-lying formations covered with thick forest. Ironwood and gum trees are among the larger trees, while jackfruit, rattan and bamboo form part of the denser undergrowth. The islands are home to crab-eating monkeys, dusky langurs, squirrels, bats, lizards and a good variety of birds (though the monkeys are shy and rarely seen by the casual observer).
But the most striking feature of these islands, at first glance, are the huge boulders that litter the western and southern shores on several of the islands. Another highlight, as the visitor soon discovers, are the white coral-sand beaches, splendidly picturesque and often deserted.
The most interesting sights, however, are to be found beneath the waves. Some of the most spectacular coral growths in the world can be found here - and the same boulders that scatter the shores have turned the waters around the Similans into an adventure playground for divers.
Underwater, meanwhile, all sorts of marine creatures have helped establish the reefs and the sandy beaches. When you climb up to Sailing Boat Rock, consider the brilliant white sand below.
This beach is in large part a product of diligent scraping and nibbling away by organisms such as the parrotfish - an average individual of which species may excrete more than 16 kilos of sand in the course of a year's lunching on hard corals. And there's plenty here to eat. The conditions for coral growth are ideal, with a minimum prevailing sea temperature of about 28oC and exceptionally clear waters. More than 200 species of hard coral alone have so far been identified in this area, while these islands have the greatest profusion of reef fish in Thai waters.
In fact, in terms of both marine life and bottom topography, there's more variety than you'll find in most other dive destinations around the world. The Similans has almost everything - coral walls (if we count Koh Bon, to the north, as one of the Similans), big rocks, huge sea fans and barrel sponges, caves, swim-throughs, and plenty of shallows for snorkelling as well. For, although the fringing waters around the islands average from 30-45m dropping down to 70-80m between islands, you'll find coral gardens in as little as six to seven metres.
At various times in the past - with sea levels fluctuating by as much as 150m with the advance and retreat of the polar ice-caps - these islands have been under water, battered by storms, covered with marine growths, visited by creatures long extinct.
Think of that when you clamber up the trail to Sailing Boat Rock, on Island No. 8, for example. As you squeeze through the crevices and archways, imagine them covered with colourful corals, sponges and algae. Where today you find birds and butterflies and squirrels, at one time dense schools, bright streams of fish instead commuted this way and that, with bigger fish and marine dinosaurs cruising through on the hunt.A variety of forces have given shape to these islands. To begin with, the Similans were intrusions, upwellings of hot magma that found their way through weak spots in the Earth's crust 100-150 million years ago, working their way through thick layers of sedimentary rock already laid down at least 100 million years earlier still. Then, unimaginably powerful movements in the crust cracked the granite substratum into blocks, preparing the way for experiments in sculptural form by wind and wave.
But the most striking feature of these islands, at first glance, are the huge boulders that litter the western and southern shores on several of the islands. Another highlight, as the visitor soon discovers, are the white coral-sand beaches, splendidly picturesque and often deserted.
The most interesting sights, however, are to be found beneath the waves. Some of the most spectacular coral growths in the world can be found here - and the same boulders that scatter the shores have turned the waters around the Similans into an adventure playground for divers.
Underwater, meanwhile, all sorts of marine creatures have helped establish the reefs and the sandy beaches. When you climb up to Sailing Boat Rock, consider the brilliant white sand below.
This beach is in large part a product of diligent scraping and nibbling away by organisms such as the parrotfish - an average individual of which species may excrete more than 16 kilos of sand in the course of a year's lunching on hard corals. And there's plenty here to eat. The conditions for coral growth are ideal, with a minimum prevailing sea temperature of about 28oC and exceptionally clear waters. More than 200 species of hard coral alone have so far been identified in this area, while these islands have the greatest profusion of reef fish in Thai waters.
In fact, in terms of both marine life and bottom topography, there's more variety than you'll find in most other dive destinations around the world. The Similans has almost everything - coral walls (if we count Koh Bon, to the north, as one of the Similans), big rocks, huge sea fans and barrel sponges, caves, swim-throughs, and plenty of shallows for snorkelling as well. For, although the fringing waters around the islands average from 30-45m dropping down to 70-80m between islands, you'll find coral gardens in as little as six to seven metres.
At various times in the past - with sea levels fluctuating by as much as 150m with the advance and retreat of the polar ice-caps - these islands have been under water, battered by storms, covered with marine growths, visited by creatures long extinct.
Think of that when you clamber up the trail to Sailing Boat Rock, on Island No. 8, for example. As you squeeze through the crevices and archways, imagine them covered with colourful corals, sponges and algae. Where today you find birds and butterflies and squirrels, at one time dense schools, bright streams of fish instead commuted this way and that, with bigger fish and marine dinosaurs cruising through on the hunt.A variety of forces have given shape to these islands. To begin with, the Similans were intrusions, upwellings of hot magma that found their way through weak spots in the Earth's crust 100-150 million years ago, working their way through thick layers of sedimentary rock already laid down at least 100 million years earlier still. Then, unimaginably powerful movements in the crust cracked the granite substratum into blocks, preparing the way for experiments in sculptural form by wind and wave.
Today, piles of curious stones, some of them as big as houses, lie as though collected and later abandoned in careless heaps by some ancient race of beachcombing giants.
Even Sailing Boat Rock, the distinctive formation teetering high above the cove on Koh Similan (Island No.8), has been shaped in this way. And boulders just like these spill in jumbled piles down beneath the surface of the sea to 35m and beyond, where submarine peaks, canyons, caves and passageways provide scuba divers with some of the most interesting submarine prospects in the world. (On the west side of the islands, currents have kept the formations clear of sand; on the coral-covered sandy slopes of the east side, the boulders have been largely buried.)
