Thailand's Marine Life

Thailand's Marine Life

Thailand's position between the Andaman Sea and the Gulf of Thailand gives it access to two distinct marine ecosystems, each with its own character, species, and seasonal rhythms. The warm tropical waters support over 2,500 species of marine fish, extensive coral reef systems, and encounters with some of the ocean's most impressive creatures — whale sharks, manta rays, sea turtles, and dugongs.

Coral Reefs

Thailand's coral reefs are among the richest in Southeast Asia, supporting extraordinary biodiversity in warm, shallow waters. Over 300 species of hard coral have been recorded across the two coasts.

Andaman Reefs

The Andaman Sea's deeper, clearer waters host Thailand's most pristine coral ecosystems:

• Similan Islands — Nine granite islands 80km offshore from Phang Nga. The underwater topography includes boulders, swim-throughs, walls, and sandy slopes covered in hard and soft corals. Visibility regularly exceeds 30 metres. Open November–May only.
• Surin Islands — Near the Myanmar border. Shallow, extensive reef flats ideal for snorkelling. Hard coral coverage is exceptional. Home to the Moken sea nomad community.
• Hin Daeng / Hin Muang — Deep-water pinnacles south of Ko Lanta. Some of the best diving in the Andaman — dramatic walls of purple soft coral, manta ray encounters, whale shark sightings.
• Richelieu Rock — A horseshoe-shaped pinnacle in the Surin group, widely considered Thailand's single best dive site. Famous for whale shark encounters (February–April). Covered in spectacular soft corals and swarming with marine life.

Gulf Reefs

Gulf waters are shallower, warmer, and slightly more turbid than the Andaman, but support healthy reef communities:

• Chumphon Pinnacle — A granite pinnacle south of Ko Tao. Schooling barracuda, giant grouper, and seasonal whale shark visits.
• Sail Rock — A massive underwater rock between Ko Phangan and Ko Tao, featuring a vertical swim-through chimney and abundant pelagic life. Often cited as the Gulf's best dive site.
• Japanese Gardens, Ko Tao — A shallow, easily accessible site perfect for beginners. Staghorn coral, anemones, clownfish, and gentle currents.
• Ang Thong Marine National Park — Protected coral systems around the 42-island archipelago west of Ko Samui.

Bleaching and Recovery

Thai corals face existential threats from rising sea temperatures. Major bleaching events occurred in 2010, 2016, and 2024, causing significant damage to shallow reef systems. Some reefs have shown strong recovery; others have not. The Thai Department of Marine and Coastal Resources monitors reef health and has implemented coral nursery programs to accelerate recovery.

Pelagic Life

Whale Sharks

The whale shark (Rhincodon typus) — the world's largest fish, reaching 12+ metres — is the crown jewel of Thai diving. These gentle filter-feeders visit Thai waters seasonally:

• Andaman Sea — February to May, particularly around the Similan and Surin Islands. Richelieu Rock is the most famous encounter site.
• Gulf of Thailand — March to September, particularly around Chumphon Pinnacle and Sail Rock near Ko Tao.

Encounters are never guaranteed, but they are regular enough to attract divers from around the world. Whale sharks feed on plankton and small fish, are completely harmless to humans, and are a profoundly moving sight underwater.

Manta Rays

Oceanic manta rays (up to 5-metre wingspan) visit Andaman dive sites seasonally:

• Hin Daeng / Hin Muang — The most reliable manta sites, February–May
• Koh Bon (Similan group) — A cleaning station where mantas come to have parasites removed by cleaner wrasses

Sharks

Despite global declines, several shark species are regularly encountered:

• Blacktip Reef Shark — Common in shallow tropical waters. Small, distinctive black fin tips. Frequently seen snorkelling at Shark Bay (Ko Tao) and around many Andaman sites.
• Leopard Shark (Zebra Shark) — Elegant, spotted bottom-dwellers. Commonly resting on sandy areas at dive sites across both coasts.
• Bamboo Shark — Small, docile nocturnal sharks found on reefs.
• Bull Shark — Rare but occasionally reported in deeper waters.

Shark populations have declined significantly due to fishing. Thai marine parks prohibit shark fishing within their boundaries, and dive tourism has created economic incentives for shark conservation.

Rays

• Blue-spotted Stingray — Beautiful electric-blue spotted rays common on sandy bottoms throughout Thailand.
• Eagle Ray — Graceful, spotted rays seen flying through open water at deeper dive sites.
• Giant Guitarfish — A ray-shark hybrid shape, increasingly rare.

Sea Turtles

Four turtle species are found in Thai waters:

The most exciting recent news: leatherback turtles returned to nest on Andaman beaches during 2020–2021 after decades of absence, likely aided by reduced tourism during the pandemic. Conservation programs now protect nesting beaches with patrols and egg collection for hatcheries.

Dugongs

The dugong (sea cow) — a gentle, herbivorous marine mammal that feeds on seagrass — survives in Thai waters in small numbers. An estimated 250 dugongs live in the Andaman Sea, primarily around:

• Ko Libong, Trang — The best chance to spot dugongs in the wild. Seagrass beds off the island's east coast support a resident population.
• Hat Chao Mai National Park — Adjacent to Ko Libong, protecting critical seagrass habitat.

In 2019, an orphaned baby dugong named Marium captured Thai hearts before tragically dying from plastic ingestion — an event that galvanised public awareness of marine plastic pollution.

Marine Conservation

Thailand has taken significant steps to protect its marine environments:

• Marine National Parks — 26 marine parks protect approximately 8,500 km² of sea and coast.
• Seasonal Closures — The Similan and Surin Islands close from mid-May to mid-October, allowing ecosystems to recover from tourist pressure.
• Maya Bay Restoration — Ko Phi Phi Leh's famous bay was closed for years to allow coral and blacktip reef shark recovery. It has reopened with strict visitor limits (no swimming in the bay, boat-free zone, time limits).
• Fishing Regulations — Commercial trawling banned within 3km of shore. Trawl bans in marine park waters.
• Single-Use Plastic Ban — Thai national parks banned single-use plastics in 2018, and nationwide plastic bag distribution restrictions were introduced in 2020.

Diving and Snorkelling Seasons