The Mayaguez affair is usually described as the last battle of American involvement in Southeast Asia, which makes it sound tidier than it was. While the crew sat under guard off this island, US forces assaulted Koh Tang, forty kilometres to the southwest, on the assumption that the sailors were being held there. They were not. Thirty-eight Americans died in that operation, fifty were wounded, three helicopters were destroyed, and three Marines were left behind alive on the beach and later executed. At half past six on the morning of 15 May the sailors here were told they could go, on condition that they first agreed to a statement saying they had not been mistreated. By quarter past seven they were aboard a fishing boat named Sinvari and heading out. They had been released unharmed, and the men sent to rescue them had already died doing it.

The island's great eastern bay is a three-kilometre crescent of white sand with a name that belongs to nobody who lives here. Saracen Bay is named for HMS Saracen, a British survey brig that charted this coast in the late nineteenth century and left its own name on the chart, as survey vessels tended to. The island's own name has fared worse. Sanloem carries a double sense in Khmer — drowsiness, and something so far out that it is hard to make out clearly — and French colonial mapmakers began mangling its transliteration in the 1800s. The variants have been multiplying ever since. Search for it today and Google Maps will offer you one spelling while Google Search redirects you to another, a small modern echo of a nineteenth-century mistake that nobody has ever bothered to correct.

Nine kilometres north to south, four across at its widest, and at one point barely a kilometre from coast to coast — Koh Rong Sanloem is mostly edge. The interior is hilly and was once almost entirely jungle, rising to 210 metres in the northwest, where one summit is known as Mont Chameau for its two humps. The two coasts behave like different islands. The eastern side faces the mainland, sheltered from the southwest monsoon, and folds itself into bays and headlands. The western side takes the weather head on and offers three yellow-sand beaches — among them Lazy Beach and Sunset Beach — backed by sandstone. Almost everything moves by boat, but the island's narrow waist is crossable, and water buffalo carts still make the haul from one sea to the other.

The administrative centre sits at the northern tip and is called M'pai Bai, which in Khmer simply means Village 23. It is the island's plainest place and, for a long time, its friendliest: family-run guesthouses, brown-yellow sand, a waterfall a short climb above the village and another hidden further along. Most of those guesthouses closed during the pandemic and never reopened. The island counted 558 residents at the 2019 census, which is a startling figure next to the number of beds now available on Saracen Bay, where villa resorts advertise air conditioning and hot showers on an island that has never been connected to the national grid. Every resort makes its own power from a generator or a solar array. There is no bank and no ATM, though most businesses will take a card, and everyone appreciates small bills.

A lighthouse stands at the southern tip, the last working relic of the French protectorate, whose road network across the interior has long since been swallowed by vegetation; the lighthouse now doubles as a military post. The Cambodian Navy keeps its main installation on Saracen Bay and smaller outposts scattered elsewhere. Administration has passed to a state-owned development corporation, which has granted concession and development rights over most of the island to a private developer. Meanwhile the island belongs, on paper, to Koh Rong Marine National Park, declared in 2018. The forest still supports great hornbills, kingfishers and ospreys, and a famously bad-tempered troop of macaques. Offshore, divers keep coming back for the small things — seahorses, nudibranchs, the fine-grained little ecosystems that live on rock and reef in water most people cross without looking down.