Similan Islands Are Open! Why January is the Best Month to Visit

If you have been waiting for the perfect time to visit Thailand's crown jewel of diving, the wait is over. The Similan Islands National Park is fully open, and we are entering the absolute peak of the season.

While the park technically opens in October, seasoned travelers know the real magic happens in the New Year. Here is why January 2026 is statistically the best month to book your speedboat or liveaboard trip to the Similans.

1. The "Glass Water" Visibility

October and November can still be recovering from the monsoon, with occasional chop and stirred-up sediment. By January, the Andaman Sea settles into a mirror-like calmness.

Visibility: Expect 30+ meters (100 feet). It is like swimming in a high-definition aquarium.

The Photos: The famous "Donald Duck Bay" water looks its bluest in January because the sky is consistently cloudless, allowing sunlight to penetrate deep into the water column.

2. It’s Manta Ray & Whale Shark Season

This is the big one for divers. January marks the start of the "Big Fish" season.

The Migration: Cooler currents bring nutrient-rich water, attracting the giants of the ocean.

Where to look: While sightings are never guaranteed, dive sites like Richelieu Rock, Koh Bon, and Koh Tachai see a spike in Manta Ray and Whale Shark encounters starting in January and peaking in February.

3. The Weather is "Goldilocks" Perfect

Thailand in January is relatively cool (by Thai standards).

Air Temp: pleasant 27°C - 30°C (80°F - 86°F).

Humidity: Low. The sticky heat of April hasn't arrived yet, making the boat ride and the hike up to the Sail Rock viewpoint much more comfortable.

4. Important 2026 Rules: How to Visit

The Department of National Parks (DNP) is strict this year. Here is what you need to know to avoid disappointment:

The Daily Cap: The park limits the number of visitors per day (3,325 people). You must book in advance. You cannot just show up at the pier in Khao Lak and buy a ticket.

No Plastic: Single-use plastics are banned. Bring a reusable water bottle.

No Fins on the Beach: To protect the coral, you generally cannot wear fins when snorkeling from the beach (only from the back of the boat).

5. How to Beat the January Crowds

Yes, January is popular. To avoid looking like a sardine in your photos:

• Stay in Khao Lak: It is closer to the pier (Thap Lamu) than Phuket. You save 2 hours of travel time, allowing you to catch the "Early Bird" boats that leave at 7:00 AM.
• Choose a Liveaboard: The best way to see the islands empty is to sleep on a boat. You get to dive/snorkel at 7:00 AM and 5:00 PM when the day-trip speedboats have all gone home.

6. Similan Islands Early Bird Day Trip

Book here: GetYourGuide Link

Pickup: Very early (approx. 04:00 – 05:00 AM) to beat the crowds.

Duration: Full day (~8-9 hours).

Highlights: Hike Sail Rock (Island 8) for the view, 2 snorkeling stops, and a picnic lunch on Island 4.

Bring: Swimwear, a towel, sunscreen, and a copy of your passport (for park entry).

Note: Speedboats are bumpy; not suitable for pregnant women or those with back issues.

Conclusion

The Similan Islands are only open for 6 months a year (closing May 15th), and the window for perfect weather is even shorter. January sits right in that sweet spot, perfect water, big marine life, and cooler air. If you are in Thailand right now, this is the trip you shouldn't skip.