When the park is open
Similan Islands National Park operates from 15 October to 15 May. From 16 May to 14 October it is fully closed — not a recommendation or a weather call, but an annual decision by the Thai national parks department. During the closure neither tourist boats nor dive boats visit the islands.
Quality varies within the season too. Underwater visibility peaks from February to April, when there is less plankton and the water is clearest. November and December give a greener, livelier underwater landscape but lower visibility. At the very start and end of the season, cancellations due to swell are more likely.
If the Similans are a must for you, schedule them for the first days of your trip. That way a weather cancellation still leaves room to reschedule.
Quotas and rules people discover at the pier
Overnight stays on the islands have been banned since 2018: tent camps and bungalows are closed. Liveaboard dive safaris are permitted but shore access is restricted. The park has introduced daily visitor quotas, so in high season boat places sell out days ahead.
Landing is allowed only on islands 4 (Ko Miang) and 8 (Ko Similan). The rest can be seen from the water only. Island 8 is the one with the sail-shaped granite boulder and the viewpoint people come here to photograph.
Plastic bottles and packaging, smoking outside designated areas, and any sunscreen containing oxybenzone or octinoxate are prohibited. Bags are spot-checked on entry. A passport or colour copy is mandatory — rangers will not let you ashore without ID.
How to get there and how the options differ
From Phuket. The speedboat takes about 2.5–3 hours each way with a stop at Tap Lamu pier in Khao Lak. It is the longest sea crossing of all our routes and it does tire you out: a 05:30–06:00 start and a return to your hotel around 18:00–19:00. In exchange, you organise nothing yourself.
From Khao Lak. If you are staying in the north or willing to overnight there, the crossing drops to 60–90 minutes and the day is markedly easier. For families with children and guests who handle swell badly, this is the better option.
Private boat. Buys you freedom of timing: leave before the main flow and reach island 8 ahead of the group boats. The difference in experience is substantial — the same locations without the crowd. Charter starts around 35,000 THB for the day.
Liveaboard dive safari, 2–4 days. A separate format for certified divers: the boat stays in the island area with 3–4 dives a day. The Similans plus nearby Ko Bon, Ko Tachai and Richelieu Rock are among the best places in the Andaman Sea for mantas and whale sharks.
What it costs and what is included
A group day trip from Phuket runs around 2,500–2,700 THB per person. The key question when comparing prices is whether the park fee is included: for foreigners it is roughly 500–600 THB and some operators collect it separately at the pier. Much of the gap between advertised prices comes down to exactly this.
A proper programme includes hotel transfer, the boat, the park fee, lunch on island 4, a snorkelling set, water and fruit. It does not include underwater camera rental, towels, alcohol or crew tips.
Budget for cash separately: there are no ATMs or card terminals on the islands, and the park cafe takes cash only.
Who this route does not suit
The Similans make for a hard day. Three hours on a speedboat in a swell feels like a fairground ride, and we do not recommend the group format to anyone prone to motion sickness, with back or neck problems, pregnant guests, or children under 5.
For similar water quality without the punishing crossing, consider the Racha Islands — only 90 minutes out — or a private boat to the Similans with a softer ride and adjustable speed.