Koh Rong Sanloem lies within Sihanoukville province's Mittakpheap district in Commune 5. Alongside its sister-island Koh Rong it has developed into a popular holiday destination for individual travelers. With respect to the island's very tiny population, the tourism sector is by 2014 the core economy.
In 1975 the crew of SS Mayaguez was shipped to Koh Rong Sanloem, detained and interrogated by Khmer Rouge soldiers during the Mayaguez incident.
The island resembles its northern sister, Koh Rong in many ways, although it has noticeably less landmass in relation to its coastline. The terrain is predominantly hilly with a few mountains of moderate size (e.g. La Chameau - The camel) and a maximum elevation of 210 m (689 ft) in the North-West. The interior is almost entirely covered in dense jungle. The coastline is characterized by a succession of sandstone rock formations and beautiful beaches. There are three yellow sand beaches at the island's long western coast. Its eastern side, facing towards the mainland and less exposed to the weather and the monsoon, is characterized by bays and headlands. A very attractive feature is the crescent shaped Saracen Beach bay with an inner diameter of around 3 kilometers. Saracen bay got its name from a British survey brig, HMS Saracen, that charted the area in the late nineteenth century. North of the island lies the uninhabited Koh Koun island, followed by Koh Rong.
There are two discernible villages on the island; one in the north, called Ma-pay Bay (means 23 in Khmer) and one in the south, called Koh Rong Sanloem Phumi Kang Khnong (kang khnong means inside in Khmer), which is little more than a fisher's hamlet. Another little hamlet is situated in the southwest, called Phumi Kang Krau (Village on the outside). There used to be a basic road network, built during the period of the French Protectorate, which is by now almost completely overgrown with vegetation. Sole reminder of this period is a lighthouse at the island's southern tip. Depending on the season, some structures that resemble a landing field near the light house are still recognizable.
Most transport is being done by boat, although the island's very narrow center permits water buffalo carts to operate. Koh Rong Sanloem is not connected to the main power grid, nor to the internet, except for the 4G tower at M'Pai bei.Smart and Cellcard SIM. There is local mobile phone coverage. The island is home to a base of and is administered by the Cambodian Navy.
As of 2017, Saracen Bay has established itself as the main tourist area on Koh Rong Sanloem, with more than a dozen bungalow and villa resorts. Accommodation and prices range from cheap dorm beds to modern villas with air-conditioning, wide-screen TV’s, comfortable beds, and en-suite bathrooms with a hot shower and a western toilet. Other notable tourist destinations include ‘Lazy Beach’ and ‘Sunset Beach’ (located on the western side of the island), and Ma-Pay Bay (located on the northern side of the island).
There are 5 main ferry services between Sihanoukville and Koh Rong Sanloem, each taking approximately 40 minutes to get to the island. All services leave from the Ochheuteal (AKA ‘Serendipity’) pier in Sihanoukville. There are also a couple of ‘Slow Boat’ services that take 1.5 – 2.5 hours. These services depart from the local port of Sihanoukville and the piers at Serendipity beach and Victory beach.
Currently there are no banks or ATMs on Koh Rong Sanloem, though its neighbouring island Koh Rong now has an ATM. Therefore, travellers to the island are advised to bring cash in order to pay for food, drinks, accommodation and any activities. Businesses that are operating on the island appreciate small denominations as it can be difficult to give change for large bills.
The island's formidable jungle is the ideal habitat for a great variety of endemic invertebrate species. Vertebrates are less abundant and, typically for island populations, are small in comparison. Amphibians and reptiles are the most numerous and the island's brooks, ponds and streams are home to a variety of small freshwater fish. Birds include the great hornbill, the kingfisher and the osprey. There is a group of macaques living on the island and rodents are very common as a consequence of human activities. Small reefs and the rocky surface of the surrounding waters are home to a remarkable variety of marine species. Divers and snorkelers regularly emphasize the abundance of delicate miniature eco-systems, seahorses and nudibranches.