Similan IslandsAbout Similan Islands
The Similan Islands are an offshore archipelago in the Andaman Sea protected as a national marine park, renowned for clear waters, coral reefs and dive sites. The group contains 11 principal islands with steep granite formations, white-sand beaches and underwater pinnacles.
Popular activities include day-trip snorkelling, multi-day liveaboard diving and guided reef visits; notable islands host basic visitor facilities, viewpoints and mooring areas for dive boats. Marine biodiversity includes reef-building corals, reef fish, and seasonal sightings of larger species such as manta rays.
The islands were designated as a national park in the early 1980s to protect marine and island ecosystems, with park management enforcing seasonal closures and visitor limits. Facilities are minimal on most islands to reduce environmental impact.
The archipelago lies off the west coast of southern Thailand within Phang Nga province in the Andaman Sea and is reachable by boat from mainland piers and nearby island marinas when the park is open.
- Seasonal access: The archipelago comprises 11 main islands protected as a national park; visitor access is seasonal, typically open November through April due to monsoon conditions.
- Diving and snorkelling: Water clarity is often excellent with strong marine biodiversity, making the islands a top destination for scuba diving and snorkelling in the Andaman Sea.
What to See#
- Koh Similan (Main island): Koh Similan (Island 4) - the largest visitor island with white-sand beaches, viewpoints and base facilities for day trips and dive boats.
- Koh Bon and Koh Tachai: Koh Bon and Koh Tachai - satellite islands beyond the main cluster noted for steep drop-offs, pelagic marine life and high-quality dive sites.
- Key dive sites: Diving and snorkel sites such as Elephant Head Rock and Richelieu Rock lie near the park and attract international scuba divers for coral reefs and large pelagic species.
Best Time to Visit Similan Islands
Best from November to April (the national park season) for diving, snorkeling and calm sea conditions.
Weather & Climate near Similan Islands
Similan Islands's climate is classified as Tropical Monsoon - Tropical Monsoon climate with consistently warm temperatures year-round. Temperatures range from 21°C to 33°C. Heavy rainfall (3406 mm/year), wettest in September with a pronounced dry season.
| Month | Comfort | Temp | Feels | Rain | Sky | Humidity | Wind | UV | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | Very Good | 21° - 32° | 26° | 32 mm | partly cloudy | 78% | 2.0 m/s | 2.1 extreme | 11.6h |
| February | Excellent | 21° - 32° | 27° | 37 mm | some cloud | 76% | 1.5 m/s | 2.4 extreme | 11.7h |
| March | Very Good | 22° - 33° | 31° | 91 mm | partly cloudy | 77% | 1.5 m/s | 2.5 extreme | 12.0h |
| April | Acceptable | 23° - 33° | 32° | 197 mm | overcast | 78% | 1.4 m/s | 2.5 extreme | 12.2h |
| May | Acceptable | 23° - 32° | 31° | 384 mm | overcast | 81% | 1.7 m/s | 2.1 extreme | 12.4h |
| June | Acceptable | 24° - 31° | 30° | 393 mm | overcast | 81% | 2.0 m/s | 2.0 extreme | 12.5h |
| July | Good | 23° - 31° | 27° | 457 mm | overcast | 81% | 1.7 m/s | 2.1 extreme | 12.4h |
| August | Good | 23° - 30° | 27° | 562 mm | overcast | 82% | 2.1 m/s | 2.2 extreme | 12.3h |
| September | Good | 23° - 30° | 26° | 572 mm | overcast | 82% | 1.6 m/s | 2.1 extreme | 12.1h |
| October | Good | 22° - 30° | 26° | 416 mm | overcast | 82% | 1.6 m/s | 2.0 extreme | 11.8h |
| November | Good | 22° - 30° | 26° | 211 mm | overcast | 80% | 1.6 m/s | 2.0 very high | 11.6h |
| December | Excellent | 21° - 31° | 26° | 54 mm | partly cloudy | 79% | 2.0 m/s | 1.9 very high | 11.5h |
How to Get to Similan Islands
The Similan Islands are reached by boat from the mainland; most visitor boats depart from Thap Lamu Pier near Khao Lak (Phang‑Nga). Speedboats and dive boats operate seasonally (main season roughly November-April) from Khao Lak/Thap Lamu to the Similan group, with typical crossings around 1.5-2 hours. Some liveaboards and day trips also operate from Phuket.
On arrival at the islands you walk short distances from the piers to beaches and viewpoints (island walking distances are generally short but involve sandy/coastal paths).
Tips for Visiting Similan Islands
- Visit during the national park season (typically November-May) when the Similan Islands are open, seas are calmer and underwater visibility is best; outside these months the park is usually closed for monsoon.
- To avoid crowded day-trip boats, opt for an early departing boat or a liveaboard/diving trip that sleeps on the islands or nearby-liveaboards concentrate on quieter dive sites and early-morning snorkels.
- Book with operators that run from Thap Lamu (Khao Lak) or reputable dive operators; they know which sites are open (Koh Bon/Koh Tachai access varies) and how to route around conservation restrictions.