If there is a single feature of south Thailand's landscape which commands one attention right from the start is the dramatic limestone crags which rise from the waters edge and valley floors to sheer vertical heights in excess of 900 meters. These butte-like crags, called "karsts", were formed 260 million years ago when a shallow sea running the entire length of south Asia, slowly built up deep deposits of shells and corals which were later buried under sediments washing in from land. Compressed deep in the earth, these calcium carbonate remains formed limestone which was thrust up above the surface when the India sub continent, collided with mainland Asia about 30 million years ago.

The collision of these two titanic plates rotated the whole of south Thailand and the Malay Peninsula clockwise and uplifted the 5,000-km ancient coral reef line. From Gualin, China to Sarawak, Borneo the limestone was thrust up above the surface like discs slipping out of places along a terribly maligned human spine. Surat Thani, Phangnga, Krabi and Trang provinces are the areas in south Thailand where karst intrusions are most pronounced.

luctuating sea levels during the ice ages allowed for extensive wave erosion of this soft sedimentary rock. For many millenniums, monsoon rains have also helped dissolve the karsts. Decomposing leaves from karst vegetation create slightly acid water which readily dissolvesthe calcium carbonate of the limestone as the water percolates down through the tiniest cracks and crevices in the rock. Rivers too have cut courses through the karsts resulting in a labyrinth of cave chambers and passageways.

Sometimes the roof of a huge cave chamber collapses and the ensuing sunlight allows colonizing plants to flourish in a hidden "garden of Eden: - a "hong". These hongs (Thai for "rooms") are one of the most fascinating features of karst topography. If the former cave floor was at, or below sea level then the hong may become a lagoon at high tide. This is the case at the Pranang "princess pool: or the lovely lagoon of koh Hong where the tide races in and out through the old cave entrance. If the old cave site is well above sea level, however, then a climax forest may ultimately grow here as in the case of Ao luk's Than Bok Koranee of Wat Tan Sua near Krabi town.

Karst support an intriguing flora and fauna, uniquely adapted to demanding habitat conditions. Vegetation on karsts has evolved the ability to withstand long period of crevices where moisture and some semblance of nutrients from decomposing leaves are available. As these plants grow and their roots and trunks swell they often sheer off part of the rock face.

Plants thus carve away at the rock in much the same way that water expanding into ice splits rock in colder climates.These vegetation in turn supports a variety of wild animal life in this very area. With luck one might be able to behold any of these wild life during a normal tour around at Phang Nha Bay National Park.

At both low tide and high tide, it is not possible to enter the hongs. Illustration of how tides affect sea cave canoe trips into the 'hongs', tunnels, and lagoons.
It is only when the tide is neither high nor low can we have access to this hidden world of limestone Emerging from the cave into an inner lagoon; this unspoiled tranquil "room" is open to the sky and as we gently paddle around observing the breath-taking scenery walls of rock covered with vegetation, bird singing and insects whining. Lawa island is located further down from Panak island. Tropical sandy beach will allow you to enjoy swimming, sunbathing, offshore canoeing or relaxing comfortably under the palm and coconut tree.