🐠 What Marine Life Can You See in the Similan & Surin Islands (and When to Go)
If you’ve ever dreamed of diving into an aquarium, the Similan and Surin Islands in Thailand are about as close as it gets.
Crystal-clear water, dramatic granite boulders, and coral gardens bursting with life make this one of Asia’s top underwater playgrounds.
Whether you’re diving or snorkeling, every season brings something special. From tiny critters to giant pelagics that make your heart race.
🌊 A Quick Overview
Both the Similan and Surin Islands are located off the coast of Khao Lak, and their marine parks are open mid-October to mid-May. During this time, visibility ranges from 20–40 meters, and the warm water (27–30°C) creates the perfect environment for a huge variety of marine life. Most people visit the islands from Khao lak on a daytrip or with a liveaboard.
From November to April, each month has its own highlights, here’s what to expect:
🐢 November – January: Crystal-Clear and Full of Life
At the start of the season, the reefs look fresh and untouched after their monsoon rest. Visibility is at its best, and the water is calm and clear. Ideal for spotting reef fish and photographing the vibrant coral gardens.
You can expect to see:
- Colorful reef fish like butterflyfish, angelfish, parrotfish, and clownfish
- Moray eels peeking from crevices
- Octopus and cuttlefish putting on their color-changing shows
- Green and hawksbill turtles cruising peacefully by
- The occasional blacktip reef shark around the shallows
It’s the perfect time for snorkelers and new divers to enjoy the Similans at their calmest.
🐠 February: Reef Magic & Schooling Fish
As the season progresses, the water stays clear, and currents become a bit stronger, which means more action underwater.
You’ll start seeing larger schools of fish and pelagic visitors moving through.
Look out for:
- Barracuda and trevally hunting around the boulders
- Napoleon wrasse gliding gracefully by
- Batfish and fusiliers schooling in huge numbers
- And if you’re lucky — a leopard shark resting on the sand!
🐋 March – April: The Season of Giants
This is when things get really exciting.
As the water warms slightly, plankton blooms begin, reducing visibility a little but attracting the biggest creatures in the Andaman Sea.
From March to April, your chances of spotting manta rays and whale sharks are at their highest.
- Manta rays are often seen at Koh Bon and Koh Tachai, where they visit cleaning stations.
- Whale sharks are most frequently seen at Richelieu Rock, near the Surin Islands, one of the best dive sites in the world for encounters with these gentle giants.
It’s also an incredible time to see massive schools of barracuda, jacks, and rainbow runners swirling in the blue.
🪸 May – October: Closed but Recovering
During the monsoon season, the Similan and Surin Islands are officially closed to visitors. The sea conditions can be rough, but this break allows marine life to rest and regenerate.
By the time the parks reopen in October, the reefs are buzzing with life again, ready for another spectacular season.
🐢 The Best of Both Worlds
Whether you’re snorkeling the shallow coral gardens of the Similans or diving the deep pinnacles of Richelieu Rock, you’ll be surrounded by thriving marine life year-round (when the parks are open).
- For crystal-clear visibility and reef life → visit November–February
- For big fish, mantas, and whale sharks → go March–April
Either way, every dive here feels like swimming through a living postcard and it’s no wonder so many divers return to Khao Lak every season to relive the magic.
