
Similan Islands Dive
Thailand's underwater paradise for serious divers
The Similan Islands aren't just another dive spot in Thailand — they're the reason serious divers make pilgrimages to the Andaman Sea. Nine granite islands rising from crystalline waters, each surrounded by some of the most pristine coral reefs you'll find anywhere in Southeast Asia. But here's the catch: you can only visit from mid-October to mid-May, when the monsoons give way to gin-clear visibility and calm seas. The Thai government shuts down access during the rough season, which means when the islands do reopen, the marine life is absolutely thriving. Whale sharks cruise the deeper sites, manta rays glide over cleaning stations, and the hard corals have had months to recover from any tourist impact. This isn't beginner territory — strong currents and deeper sites mean you'll want your Advanced Open Water certification before you arrive.
Culture & Context
LOVED TO DEATH
The name "Similan" comes from the Yawi (Malay) word meaning "nine," a reference to the original nine islands that made up the park when it was first established. Two more were added in 1998, Ko Bon and Ko Tachai, bringing the total to eleven. Ko Tachai was permanently closed in 2016 after coral damage from overcrowding became irreversible.
That closure stings a bit for anyone who visited before. In 2018, the park authorities also banned all overnight camping and bungalow stays on the islands entirely. What was once a place where you could pitch a tent on the beach and wake up to an empty bay is now strictly day-visit only.
The daily visitor cap sits at around 3,325 people. That sounds like a lot until you realize it used to be 7,000 on peak days. The park's current rules — no single-use plastics, no drone flights without a special permit, no feeding wildlife, reef-safe sunscreen only — reflect how close the reef came to being loved to death.
Locals and dive operators take these rules seriously. Most tour crews brief guests on coral etiquette before anyone hits the water.
Local Customs
REEF-SAFE OR STAY HOME
No overnight stays on the islands. This has been the rule since 2018. Anyone selling you a camping package to the Similans is either confused or lying..
Reef-safe sunscreen is expected, not optional. The park has educational boards explaining which chemicals destroy coral. Avoid products containing Oxybenzone, Octinoxate, 4-Methylbenzylid Camphor, and Butylparaben.
Apply it at least 20 minutes before entering the water.. No single-use plastics or foam containers allowed anywhere in the park. Bring a reusable bottle and pack your snacks in non-plastic containers..
Drones are forbidden without a special permit from the National Park authority. Enforcement has gotten stricter. Don't risk it..
No touching, standing on, or disturbing coral. No feeding the fish. No collecting shells, rocks, or any natural material from the islands..
Smoking is restricted to designated areas only on the island. This is actually enforced.. The wai greeting (hands pressed together like prayer, slight bow) is the standard respectful hello when meeting locals.
You don't have to initiate it, but always return one if it's given to you.. Remove shoes before entering any temple or someone's home. It's automatic behavior for locals and noticed when tourists skip it..
Divers must hold a valid certification before entering the park. Entry-level courses (Discover Scuba, Open Water lessons) are banned from being conducted within the park boundaries.
Safety
ROUGH WATERS, CLEAR RULES
The speedboat ride from Thap Lamu Pier to the islands runs 60-90 minutes across open Andaman Sea. On choppy days, it's genuinely rough. Speedboats are not recommended for pregnant women, infants under one year old, or anyone with serious back problems.
Take motion sickness medication before you board — once you start feeling sick on open water, it's hard to recover. Bring it from home; most tour operators provide some, but you want your own dose. The daily visitor cap (around 3,325 people) means popular days, especially during Christmas, Chinese New Year, and Songkran, can sell out.
Book through the DNP e-ticket system or a reputable operator well ahead of time. Ko Tachai (Island #11) is permanently closed to all visitors and has been since 2016. Don't believe anyone who says otherwise.
Leave valuables in your hotel safe; there's nowhere secure to store them on an all-day boat trip. Water clarity is exceptional but currents can pick up around headlands. Listen to the guide's briefing on snorkel zones — they're not being cautious for fun.
Getting Around
SPEEDBOAT OR CATAMARAN
All boats to the Similan Islands depart from Thap Lamu Pier, located roughly 8km south of Khao Lak and about 70-100km north of Phuket. From Phuket hotels, expect a 1.5-2 hour van transfer to the pier before you even get on a boat.
From Khao Lak accommodations, it's a quick 20-minute drive. That difference matters on a day that already runs 10-12 hours. Speedboats carry around 35-40 passengers and take 60-75 minutes to reach the islands.
They're fast and time-efficient but loud and bouncy in anything but calm conditions. Catamarans take closer to 2 hours but offer a smoother, more stable ride. They're the smarter choice for families with young children, older travelers, or anyone prone to seasickness.
Speedboat tours start around 2,500 THB; catamaran tours run 3,100-4,000 THB. The price gap is worth it if motion sickness is a real concern. On the mainland in Khao Lak, songthaews (shared pickup truck taxis) are the local transport option and far cheaper than private transfers.
For getting between the Khao Lak areas, renting a scooter (around 200-300 THB per day) gives you full freedom. Phuket International Airport (HKT) is the nearest international airport, roughly 80-100km south of Khao Lak.
Useful Phrases
Itineraries coming soon
We're working on adding amazing itineraries for Similan Islands Dive. In the meantime, try the app to create your own!
Money-Saving Tips
- 1.Book dive packages in advance online for 10-15% discounts compared to walk-in rates
- 2.Stay in Khao Lak rather than expensive Phuket resorts — you'll save 3,000+ baht per night
- 3.Eat at local Thai restaurants instead of hotel dining — meals cost 150-300 baht vs 800+ baht
- 4.Join group dive trips rather than private charters — splits the boat cost among 15-20 divers
- 5.Bring your own mask and fins to avoid 200 baht daily rental fees
- 6.Book liveaboard trips during shoulder season (November or April) for 20-30% savings
Travel Tips
- •Get Advanced Open Water certification before arriving — many sites require it due to depth and currents
- •Pack seasickness medication even if you don't usually get sick — 2-hour boat rides in swells are different
- •Bring a reef-safe sunscreen — regular sunscreen is banned in the national park
- •Book accommodation within walking distance of Nang Thong Beach for easy access to dive shops
- •Download offline maps of Khao Lak — WiFi can be spotty and you'll need directions to dive shops
- •Pack a warm layer for early morning boat departures — it gets surprisingly cool at 6 AM
- •Bring a waterproof bag for your phone and valuables during boat transfers
- •Check your dive insurance covers Thailand and depths up to 40 meters before traveling
Frequently Asked Questions
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