Eight islands lie twenty kilometers east of Hoi An, ringed by coral beds that UNESCO designated a World Biosphere Reserve in 2009. The Cham Islands shelter four hundred species of reef fish and one hundred thirty-five coral varieties, concentrated in shallow gardens that reach full visibility between April and September. Vietnamese authorities capped daily visitor numbers at three thousand in 2011, enforcing a zoning plan that reserves the northern coastline of Hon Lao—the largest island—for scientific monitoring while opening southern bays to supervised snorkeling. The marine park generates fifteen billion Vietnamese dong annually, half of which funds ranger patrols and mooring-buoy systems that prevent anchor damage to the reefs. Fishing communities on Hon Lao and Hon Dai transitioned from trawling to eco-tourism between 2010 and 2015, converting wooden boats into passenger shuttles and establishing homestays near Bai Lang village. The shift followed a decade-long decline in tuna and grouper stocks, documented by the Nha Trang Institute of Oceanography in a 2008 biodiversity survey that recorded forty percent reef degradation from dynamite fishing. Conservation measures since then—including a no-take zone covering twelve square kilometers—have restored hard coral cover to sixty-one percent as of 2024. Private snorkeling excursions depart Cua Dai pier at dawn, crossing the channel in thirty to forty minutes depending on sea state. Operators hold permits from the Cu Lao Cham Marine Protected Area management board, limiting group sizes to fifteen passengers per vessel to reduce reef trampling. Most itineraries allocate two hours for snorkeling across two sites: Bai Chong on Hon Lao's southeast coast, where elkhorn coral formations rise three meters from sandy floors, and Bai Ong near Hon Tai, a drift site favored for schools of fusiliers and occasional hawksbill turtle sightings. Surface water temperature holds steady at twenty-eight degrees Celsius through summer, dropping to twenty-four in January and February when northeast monsoons reduce visibility to eight meters. Cham island snorkeling private tour operators include gear rental, reef-safe briefings, and the ninety-thousand-dong conservation fee—seventy thousand for island entry, twenty thousand for environmental monitoring—in quoted prices. Speedboat transfers shave fifteen minutes off the crossing compared to older wooden ferries, a advantage that extends bottom time during morning slack tides when current along the outer reefs drops below half a knot.