Hong Island sits 25 kilometres west of Ao Nang, its inner lagoon encircled by vertical limestone walls that rise 120 metres from water so clear the coral formations beneath longtail boats cast shadows on the sand six metres below.
The archipelago forms the centerpiece of Than Bok Khorani National Park, a 104-square-kilometre marine reserve gazetted in 1991 to protect the Andaman's karst ecosystems and the reef networks that fringe every island. The lagoon itself is a drowned sinkhole, accessible only through a narrow channel that tour boats navigate at low speeds to avoid disturbing the staghorn coral colonies that line the passage.
Krabi's longtail boats have served these routes since the 1970s, when fishermen began ferrying Bangkok holidaymakers to beaches the road network could not reach. Today the hong island tour from ao nang operates year-round, with departures timed to the Andaman's tidal rhythms — morning trips enter the lagoon at mid-tide, when water depth allows passage without exposing the fragile reef crests to hull damage. Speedboat operators joined the route in the late 1990s, cutting travel time to 35 minutes and enabling multi-island itineraries that pair Hong's lagoon with Lading Island's sand spit and Pakbia Island's mangrove channels. The park authority limits daily vessel entries to 80, a quota introduced in 2018 after marine biologists documented coral bleaching in the lagoon's southwest corner.
The archipelago's geology tells a 260-million-year-old story. These karst towers began as Permian limestone deposited on an ancient seabed, then uplifted and sculpted by monsoon rains into the fluted cliffs that define the Andaman coast. Phang Nga Bay's famous pinnacles share the same origin, but Hong's islands cluster more tightly, creating sheltered corridors where hawksbill turtles nest between May and October. The park's conservation fee — 300 baht per international visitor — funds reef monitoring stations and the seasonal closure of nesting beaches, measures that have stabilised turtle populations after decades of decline. Snorkeling reefs fringe the western shores, where visibility averages 12 metres outside the monsoon months and schools of sergeant majors and parrotfish navigate the coral bommies that rise like submerged towers from the seabed. The best hong island tour from ao nang tours depart by 08:00, reaching the lagoon before the midday sun flattens the water's gradient from jade to cobalt.
6 hr
