Thailand · Andaman Sea

Richelieu Rock

Peak pelagic and whale shark timing usually falls in the open-park season.

Richelieu Rock is a horseshoe-shaped pinnacle in the Andaman Sea that rises just to the surface — a single seamount draped in purple soft coral with whale sharks, barracuda schools, frogfish, and an extraordinary macro layer. Jacques Cousteau called it one of the world's top ten dives.

Good season

Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

October to mid-May only (Similan Marine Park is closed in monsoon). February–April is peak for whale sharks.

Trip duration

Day-trip from Khao Lak (long day) or 4–6 night Similan liveaboard.

Dive style

Multiple loops around the pinnacle; moderate current possible.

Dive level

Advanced Open Water recommended for the current and depth.

Reef health

What you’ll actually find
Mixed

Some loss since the 2010s, but the reef still has plenty to dive. Pick depth and shoulder-season carefully.

Coral reef health

How is this calculated?
A decade ago
Survey 2014
39%
Today
Survey 2024
36%

On current trend, no live coral by ~2144. Losing about 0.3% cover per year — roughly 120 years of reef left to see if nothing changes.

Heat stress right now

Watch

Mild warmth. Worth watching — no bleaching yet.

NOAA Coral Reef Watch · updated May 2026 · 5.2 °C-week heat dose

What to expect on a dive

Pinnacle dive — fish life and macro, not extensive coral. Whale-shark season Feb–Apr is the highlight.

Sources, methodology, and the raw numbers

Raw observed numbers

  • Coral cover: 36% (survey Sep 2024, GCRMN / DMCR Andaman Sea transect)
  • Bleached: 9%
  • Recent mortality: 3%
  • Andaman Sea — observed condition reflects the slow loss regional pattern.

Raw thermal numbers

  • NOAA CRW alert level: Watch
  • Degree Heating Weeks: 5.2 °C-wk
  • SST anomaly: +0.5 °C

How we summarise this

Observed coral cover, bleaching, and mortality come from named in-situ surveys with a stated date and method — they describe one snapshot of one reef and do not extrapolate to neighbouring sites. Current thermal stress is satellite-derived from NOAA Coral Reef Watch at ~5 km resolution; it indicates risk, not observed coral damage. We deliberately separate observed condition, current thermal stress, and projection — and we never publish a projection without a documented model and uncertainty.

Sources

Reef condition changes year to year. If you visit, consider supporting responsible-travel and conservation operators on the ground.

Pressure on this reef

Protection · fishing · what you can do

Protected-area status

Strict MPA

Inside a strict marine protected area with active enforcement.

Fishing pressure

Moderate fishing pressure

Dominant pressures

  • tourism overcapacity
  • warming
  • anchor damage

3 Green Fins-verified operators known at this location.

What you can do

Similan / Surin national parks close seasonally to allow reef recovery. Liveaboards only. Choose operators that respect closures.

Protection status sourced from Protected Planet / WDPA and refined with Marine Protection Atlas. Fishing pressure proxy is Global Fishing Watch AIS data. See the methodology for what these sources can and can’t prove.

Dive sites here

2 curated

Gear

What to bring

Basic kit

Site-specific add-ons

Some dive sites here call for extra gear. Check the individual site page for full context.

  • SMBOpen-ocean pinnacle, all dives end with drift surface. · Richelieu Rock
  • Reef hookHook in on up-current side to watch the action without finning. · Richelieu Rock

What divers say

Richelieu in March with a whale shark sliding around the rock — I've chased that dive every year since.
Repeat liveaboard guest