The Cham are a Malayo-Polynesian people who settled in central Vietnam around 200 BCE and built the Champa Kingdom in the Hue region around 200 CE. That kingdom endured, through conquest and contraction, until 1835. At its peak, from the 7th to the 10th centuries, the Champas controlled the spice trade routes connecting Indonesia's Spice Islands to China, India, and the Persian Gulf — routes they navigated in vessels similar to those still working Hội An's waters today. Hội An itself, the commercial capital of Champa, stood on a par with Malacca and Macau as a regional port from the 16th through 18th centuries. Chinese, Japanese, and other merchants would sail south on the northeast monsoon in autumn and winter, then wait in Hội An for the winds to shift south in spring before sailing home. Some stayed long enough to build houses. The Cham Islands anchored this entire world: leeward anchorage at Bai Lang Bay, deep enough for large vessels unable to cross the shallow river inlet, with lighters ferrying cargo ashore.

The archipelago covers 235 square kilometers of sea and island, dominated by Hon Lao — the largest and only inhabited island, 1,317 hectares, with a summit at 517 meters. The other seven islands, including Hon Cu, Hon Kho, Hon La, and Hon Dai, rise between 70 and 200 meters and are uninhabited. Hon Lao holds two villages: Bai Lang, the larger, and Bai Huong. The island has no rivers, only rocky freshwater streams running through natural forest that covers about 25 percent of the land. Wild monkeys inhabit these forests. Bird's nest collectors harvest swiftlet nests from the east face of Hon Lao and from the rocky outcrops of Hon Co — nests that sell, in the premium end of the market, for around US$4,000 per kilogram. The marine environment around the islands is rich: surveys have found 135 coral species across 35 genera, 202 fish species, 84 mollusk species, four lobster species, and six coral species first identified in Vietnamese waters here.

In May 2009, UNESCO designated the Cu Lao Cham–Hoi An region a Biosphere Reserve, a status meant to ensure sustainable management of the environment and local communities. The designation had the opposite immediate effect. Mass tourism, primarily from domestic visitors from Hanoi and other northern cities, exploded almost as soon as the UNESCO label was attached. The islands were fished out in the summer of 2010 as visitor numbers overwhelmed the marine ecosystem. By 2011, according to observers on the ground, the situation had worsened further. The bird's nest industry, one of the most lucrative operations in the islands, employs no local residents. The infrastructure remains poor: pier facilities at Bien Phong are inadequate, and in February 2012 at least seven people drowned in a boat accident at the river inlet. Climate change compounds the pressure; beaches along the mainland coast have lost roughly 30 meters of sand since 2005, and the window of calm weather suitable for visiting the islands has shortened.

The journey to the Cham Islands is itself a lesson in seasonal rhythm. From September through December, the northeast monsoon makes the crossing almost impossible — breaking swells over a river mouth that averages only 90 centimeters deep. January through May is sometimes accessible; June through August, when the monsoon reverses and winds calm, is the reliable season. Each morning around 07:30, weather permitting, a wooden ferry leaves Hội An's public pier for Bai Lang village on Hon Lao — a two-hour crossing. Speedboats from Cua Dai Beach cut that to 30 minutes but cannot operate in rough weather. The coral reefs are at their best for snorkeling in June through August, when calm water settles the sediment and sunlight penetrates. Permits are required to snorkel in the Marine Protected Area; the fee supports MPA management. The islands reward patience and timing — which has always been true of this coast.