The Mu Koh Surin Marine National Park is located 80 km (42 n. miles) due west off Ranong province on the west coast of Thailand.
	Its five granite islands sit in 135 sq.km (80 sq. miles) of water. The largest, Koh Surin Nua, has an area of 19 sq.km (11 sq. miles) and its highest point is 240 m (800 ft) above sea level.

To its immediate southwest lies Koh Surin Tai - the strait between the two is only 200 m (220 yd) wide and can be crossed by foot during low tide. Koh Surin Tai is somewhat smaller with only 12 sq.km (9 sq. miles), and its highest point is 350 m (1,169 ft) above sea level.

Both of these islands are covered with verdant primary forest. The supporting canopies average 32 m (104 ft) in height. Amidst the forest area there are a few fruit trees and a coverage of secondary growth, the primary forest having suffered not only from harsh monsoon conditions, but also from some logging during the 1960s.

The only residents on Koh Surin Nua are the National Park officials. Koh Surin Tai has some small communities of Chao Ley sea gypsies on some of its eastern beaches.

The Mu Koh Surin Marine National Park sites are visited by liveaboard excursions from Phuket. Many of the sites follow fringing reefs which slope gently to the seabed; others take you around small islets and along the wall of sheer submerged pinnacles.

Two local sites are as diverse as they are interesting. Koh Tachai features a series of multi-level reefs, each one different from the others in both its formation and its resident marine life. Further south, the rocky outcrop of Koh Bon features regular visits from mantas and whale sharks.

The coral and marine life of Mu Koh Surin are now, thankfully, under protection, which was recently extended to include Richelieu Rock, but there is till evidence of damages caused by a range of different fishing techniques - for example, dynamite fishing has certainly left its mark.