The Similan Islands are a national marine park roughly 60–100km north-west of Phuket, known for some of Thailand's clearest water and best diving.
Seasonal access
The park typically closes for part of the green season (roughly mid-May to mid-October, dates vary by year) to let the ecosystem recover from monsoon conditions — this is worth confirming directly before booking, since it affects nearly half the calendar. See our weather guide for the broader seasonal pattern behind this closure.
Day trip vs liveaboard
A day trip from Phuket involves a long speedboat transfer each way, leaving a shorter window at the islands themselves. Liveaboard dive boats (2–4 nights) spend far more time in the water and reach dive sites a day trip can't cover.
What you'll see
Granite boulder islands, powder-white beaches and coral reefs with regular sightings of reef sharks, turtles and (seasonally) manta rays at some sites.
Reef safety while you're there
Given the Similan reefs' sensitivity, reef-safe sunscreen and not touching coral matter more here than almost anywhere else on a standard Phuket itinerary — see our reef safety guide for specifics.