Say the name slowly and it begins to repeat itself. Koh is Khmer for island. Poulo arrived from Malay, a cousin of the Cham word pulo, which also means island. Somewhere in the long traffic of traders, fishermen, mapmakers and colonial surveyors crossing the Gulf of Siam, each new arrival heard the local word for what he was looking at, assumed it was part of the name, and bolted his own word onto the front. What survives on the charts is a stacked redundancy: Wai Island Island. Nobody lives out here to object. Ninety-five kilometres southwest of the Cambodian coast, two wooded ridges break the surface of open water, uninhabited and rock-fringed, far enough from anywhere that the twentieth century largely overlooked them - until four days in May 1975, when this became the most closely watched patch of sea on Earth.
The Wai Islands add up to less than four square kilometres of land - 3.9, to be exact - strung along 14 kilometres of coastline. Each island runs roughly five kilometres end to end and never exceeds about a kilometre and a half across, so from the air they read as a pair of green commas laid parallel on blue. They sit 1.4 kilometres apart, divided by a channel three-quarters of a mile wide and only about forty feet deep, shallow enough that the water over it shifts colour on a bright day. The western island climbs to roughly 100 metres at its southwestern end. The eastern one tops out near 61 metres and is fringed with rock, which is part of why nobody ever built a village here. Officially the islands answer to Kampot Province, though the nearest mainland is Preah Sihanouk. The recorded population is zero. Khmer, Chvea and Cham people have all been associated with these waters historically, but the islands themselves have stayed empty.
Emptiness has never made the Wai Islands unimportant. Quite the opposite. In 1939 Jules Brevie, Governor-General of French Indochina, drew a line across the Gulf of Thailand to sort out which colonial administration handled which islands - a purely bureaucratic convenience, never intended as a border, and never actually carried out as a formal allocation. When French Indochina dissolved, that unfinished line was left behind like a half-built bridge. Cambodia, Thailand and Vietnam each measured the reach of their territorial waters from these islands using different methods, and their claims overlapped. That is the quiet, unglamorous reason a pair of uninhabited ridges matters: a rock with a name on it extends a nation's water. The oddity is easiest to see in the neighbourhood's most famous anomaly - Phu Quoc, a large island lying closer to the Cambodian shore than the Vietnamese one, yet Vietnamese all the same, because of where a Frenchman put his pen.
On 12 May 1975, twelve days after Saigon fell, the American container ship SS Mayaguez was steaming through these waters. At 14:18 a Khmer Rouge Swift boat closed on her, fired across her bow, then fired a rocket-propelled grenade. Captain Charles T. Miller sent an SOS and stopped his ship. Seven Khmer Rouge soldiers came aboard; another twenty or so joined them off Poulo Wai around 16:00. Fifteen minutes later the crew were transferred onto two fishing boats and taken toward Koh Tang, the island just to the north. Washington, three weeks into peacetime, reacted as though the war had never stopped. On 15 May, US Marines assaulted Koh Tang looking for men who by then had already been moved to the mainland. Fifteen Marines and Air Force crewmen died in the fighting. Three more Marines were left behind in the withdrawal and later executed - a mistake discovered far too late to fix. The Mayaguez crew were released unharmed the same day.
Barely a month after the Americans left, the islands changed hands again. Vietnam People's Army forces seized the Wai Islands in June 1975, and Khmer Rouge and Vietnamese troops fought each other over ground the two movements had been nominal allies on weeks earlier. The Vietnamese pulled out in August. Nothing was settled by any of it; the clash was an early tremor of the war between the two communist states that would break open in full within three years and end with Vietnamese tanks in Phnom Penh. Seen from these two ridges, 1975 was not a year in which one war ended. It was a year in which one war ended and the next one started, with only a few weeks of quiet water in between.
For decades afterward, the Wai Islands were simply off-limits. That has eased. Organised excursions now run out from the Cambodian coast, though the distance imposes its own rule: 95 kilometres is too far to go and return in a day, so anyone who comes has to stay the night. There are no hotels, no village, no lights. Visitors sleep on the beach or on the boat, with reef in the shallows, forest running down to the sand, and the eastern island's rocky skirt catching the swell. It may be the only place in Cambodia where the standard tourist experience is to be the only people on an island - and to lie awake listening to water move through a channel that three countries once argued about.
The Wai Islands lie at 9.917N, 102.900E in the Gulf of Thailand, 95 km southwest of Cambodia's Preah Sihanouk coast. From cruising altitude they appear as two narrow parallel green ridges roughly 5 km long, separated by a bright shallow channel about 1.4 km wide - an unmistakable signature in otherwise empty water. The western ridge is the higher of the two at about 100 m; the eastern is lower and rock-fringed. Koh Tang lies to the northeast. Best viewing altitude is 5,000-8,000 ft, low enough to resolve the reef colour on the channel. Nearest airports are Sihanouk International (VDSV/KOS) roughly 100 km to the northeast and Phu Quoc International (VVPQ/PQC) about 120 km to the east. Expect excellent visibility in the dry season from November to April, with heavy convective cloud and reduced ceilings during the southwest monsoon from May through October.