Similan Islands Guide

The park follows the same cycle every year. It opens on 15 October and closes on 15 May, and the national parks department closed it this year from 15 May to 15 October 2026 for the monsoon and for the reefs to recover. Opening is on 15 October 2026 for the 2026–27 season. In a stormy year it can close a few days early, and on rough days the boats don't sail.

The best months are December to March, with the calmest water and the best visibility. Late October and November can still bring swell. For divers, the manta season at Koh Bon is roughly February to April. Inside the park, visits run from 08:00 to 16:00, and the total is capped at 3,850 people a day.

The park's eleven islands are numbered from south to north, and the tours use the numbers more than the names. Islands 1 to 3 aren't on the tour routes, and almost every day trip follows the same pattern of two landings and two snorkel stops.

From Khao Lak, the van collects you between about 06:30 and 07:30, you check in at Thap Lamu pier around 08:00, and the boat crosses in about an hour and a quarter. Most tours land at Island 8 and Island 4, snorkel at Islands 9 and 7, serve lunch on Koh Miang, and leave the islands between 15:00 and 15:15, back at the pier by about 16:30 to 17:30. The prices on the operators' own sites run about ฿3,700–4,200 with the park fee for a speedboat or catamaran, and about ฿5,900 for an early-bird boat that reaches Donald Duck Bay before the crowds.

From Phuket, it's the same boat with a road transfer on each side. Pickups start at about 05:30 to 06:30, and you're back at your hotel after 18:00. It's doable for a one-off, but with two hours in a van each way I'd rather spend a night or two in Khao Lak, which is 80 to 100 minutes north of Phuket airport by car. Book a few days ahead from December to March, check whether the ฿500 fee is included, and take a catamaran if you're prone to seasickness.

The Similans are one of Thailand's two great dive destinations, along with Koh Tao in the Gulf, and the one for experienced divers. The granite boulders make swim-throughs and canyons, and the best-known sites are Elephant Head Rock, between Islands 7 and 8, with currents and depths past 40 meters, Christmas Point off Island 9 with whitetip reef sharks, and Koh Bon's ridge for mantas from about February to April. Richelieu Rock, the famous whale-shark site, is in the separate Surin park to the north, and most longer liveaboards include it.

A two-dive day trip from Khao Lak costs about ฿6,300 including the ฿700 a day diver's park fee and gear, or about ฿7,900 for three dives. Liveaboards are the way to dive the outer sites at dawn and dusk. On the operators' 2026–27 rate sheets, a three-day, three-night trip with nine dives runs about ฿18,000 to ฿26,000 plus park fees, and four- and five-day trips that reach Richelieu Rock run about ฿22,000 to ฿56,000 depending on the boat. Corals here were hit by the 2024 mass bleaching across the Andaman, and many have reportedly recovered.

Khao Lak is the base, a 20 km strip of low-rise resorts and long beaches on the mainland, 15 to 40 minutes from Thap Lamu pier depending on your hotel. Every Similan tour picks up there, and it's an hour closer to the islands than Phuket at each end of the day. From Phuket airport it's 80 to 100 minutes by road, and the Phuket to Khao Lak guide has the taxi counter fares, the bus and the vans.

Mu Ko Surin National Park, further north near the Myanmar border and reached by boat from Khuraburi, runs on the same October-to-May season and charges the same ฿500 fee. It's known for the shallow coral gardens off its beaches and the Moken sea-nomad village on Koh Surin Tai, and unlike the Similans it still has the park's own bungalows and tents. Some Khao Lak operators run combined Similan and Surin dive days, and the longer liveaboards visit both.