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Similan Islands Liveaboard Trip Report December 2023

Uncharacteristically cold waters during December 2023 in the Similan Islands brought a whole bunch of new marine life up from the deep. Here’s some photos from a very chilly liveaboard trip

Marble Ray on the move over boulder
Marble Ray on the move over boulder © chris@divehappy.com

Cold, cold, so cold. Diving in the Similan Islands typically involves balmy temperatures of 28 to 29 degrees celsius in the water. Many divers just go with boardshorts and a thin neoprene top it’s so warm. That was definitely not a wise idea during December 2023, when temperatures in the water dropped to a chilly 23 degrees.

Jacks over the top of Richelieu Rock
Jacks over the top of Richelieu Rock © chris@divehappy.com

It obviously wasn’t 23 degrees as soon as you hit the water – the real cold temperatures were reserved for going down below 15 metres. That’s where you can encounter the joy of the Green Monster, the local name for the cold current which sometimes rolls in from the deep, making the water feel like you’re looking at a shimmering mirage but with a drop in temperature that definitely lets you know you’re not in the desert.

Richelieu soft corals and glassfish
Richelieu soft corals and glassfish © chris@divehappy.com

The upside of the the downturn in temperature is that it means a lot of sharks and rays come up shallower than normal, straying into the 30 metre and above zone divers typically wander around in.

Barracuda from below, Richelieu Rock
Barracuda from below, Richelieu Rock © chris@divehappy.com

As such we had sightings of rays on several dives, including an absolute whopper of a blotched fantail ray, easily a metre across its main body, resting between the big rocks at Christmas Point, along with a smaller, more active marble ray further into the deep.

Christmas Point big blotched fantail ray resting
Christmas Point big marble ray resting © chris@divehappy.com

The cold water certainly hadn’t scared off the usual suspects to be found on a Similans liveaboard – Richelieu Rock in particular was absolutely epic for fish action, with electric activity all over the pinnacle.

Richelieu Rock anemones with cyclone of glassfish
Richelieu Rock anemones with cyclone of glassfish © chris@divehappy.com

Glassfish in their thousands shimmered around the soft corals, arcing like a silver ribbon just for a moment and then shape shifting as one.

Fusiliers running over the anemones, Richelieu Rock
Fusiliers running over the anemones, Richelieu Rock © chris@divehappy.com

Hundreds-strong schools of fusiliers would sweep across the famous soft corals at the top of the rock, momentarily blocking out the sun because there was so many.

Jacks, Richelieu Rock
Jacks, Richelieu Rock © chris@divehappy.com

Recommended Similan Liveaboards October 2025 to May 2026

Blue Dolphin Liveaboard

Blue Dolphin Liveaboard A mid-range liveaboard with 7 cabins for 16 people. Check availability and pricing

The Phinisi Liveaboard

The Phinisi Liveaboard A Similan mid-range liveaboard with 7 cabins for 18 people.Check availability and pricing

Smiling Seahorse Liveaboard

Smiling Seahorse Liveaboard A mid-range liveaboard with 8 cabins for 16 people. Check availability and pricing

The Junk Liveaboard

The Junk Liveaboard A mid-range liveaboard with 6 cabins for 18 people. Check availability and pricing
 

Fusiliers running
Fusiliers running © chris@divehappy.com

By way of complete contrast to Richelieu, Ao Pakkad in the Surin Islands provided for a beautiful and serene early morning dive before heading to the mayhem of the Rock.

Ao Pakkad staghorn and fish
Ao Pakkad staghorn and fish © chris@divehappy.com

Ao Pakkad is a huge hard coral garden that has been left largely untouched. The corals here are super old, super dense and largely pristine – it is a joy to see a reef so untouched. It’s super shallow, from a metre down to 10 metres, and so the sunlight streams down onto the corals too.

Glassfish cyclone over table coral, Ao Pakkad
Glassfish cyclone over table coral, Ao Pakkad © chris@divehappy.com

The garden is characterised by corals growing on top of corals, all shapes and sizes encroaching and entwining on each other.

Ray and two divers
Ray and two divers © chris@divehappy.com

The cold water had brought rays up even into the shallows of Ao Pakkad, with several of them sat on the sand where the reef runs out.

Ao Pakkad reef layers
Ao Pakkad reef layers © chris@divehappy.com

The coral layers of Ao Pakkad’s reef can be super colourful

Staghorn with glassfish
Staghorn with glassfish © chris@divehappy.com

There are healthy outcrops of staghorn corals which glassfish love to gather around, along with big table corals that also provide shelter.

Glassfish over table coral, Ao Pakkad
Glassfish over table coral, Ao Pakkad © chris@divehappy.com

If you're interested in doing a Similan liveboard yourself, see Diving The Similan Islands: A Quick Guide for a breakdown of how a liveaboard trip works and why the Similans are so special for diving.

Emperorfish over the reef at Richelieu Rock
Emperorfish over the reef at Richelieu Rock © chris@divehappy.com

Despite it being quite murky at Richelieu Rock, it was spectacular in terms of the sheer amount of fish gathered there.

Jacks running, Richelieu Rock
Jacks running, Richelieu Rock © chris@divehappy.com

Epic runs of emperorfish across the rock and jacks running from out of the depths

Glassfish cyclone in front of Richelieu Rock pinnacle
Glassfish cyclone in front of Richelieu Rock pinnacle © chris@divehappy.com

While there are always a lot of glassfish at Richelieu, on one dive there were so many you couldn’t see the base of the rock – thousands upon thousands of them like a cyclone sweeping through.

Fish stampede at Richelieu Rock
Fish stampede at Richelieu Rock © chris@divehappy.com

The jacks and rainbow runners like to hunt together in hundred strong packs – being in the middle of this as the fish shoot past you inches away from your face is not an experience you’re likely to forget.

Two rays, Richelieu Rock
Two rays, Richelieu Rock © chris@divehappy.com

The cold water was bringing up more rays from the depths to Richelieu’s flat sand around the pinnacle. At one point we saw a group of five of them all resting on the sand.

Glassfish and soft coral Richelieu Rock
Glassfish and soft coral Richelieu Rock © chris@divehappy.com

And despite the murky conditions, there was still sunlight and Richelieu’s signature soft red corals bursting with colour near the top of the rock.

Fish run from the depths, Richelieu Rock
Fish run from the depths, Richelieu Rock © chris@divehappy.com

The runs from the jacks and rainbow runners was not a one-off, blink and you’ll miss it kind of event.

Fish stampede, Richelieu Rock
Fish stampede, Richelieu Rock © chris@divehappy.com

They do this regularly – if you stay in one place on the dive site you’ll probably see them run four or five times.

Lionfish, West of Eden
Lionfish, West of Eden © chris@divehappy.com

Lionfish get a raw deal because they’ve accidentally invaded the Caribbean, but they’re great subjects for photography.

Emperorfish, West of Eden
Emperorfish, West of Eden © chris@divehappy.com

These two emperorfish were too interested in finding food to be bothered by the camera.

Sweetlips, Koh Bon
Sweetlips, Koh Bon © chris@divehappy.com

The cold water had also brought a big school of sweetlips up to around 30 metres at the end of Koh Bon ridge – more used to seeing these guys in such big numbers in Indonesia.

Two Cuttlefish, Koh Bon Bay
Two Cuttlefish, Koh Bon Bay © chris@divehappy.com

When the current’s too strong and you get pushed off Koh Bon’s ridge into Koh Bon Bay, there’s still some surprises around, like these two cuttlefish and a puffafish getting cleaned.

Puffa fish with cleaner wrasse, Koh Bon
Puffa fish with cleaner wrasse, Koh Bon © chris@divehappy.com

Similan Liveaboards Overview

  • Luxury Similan Island Liveaboards
  • Mid Range Similan Island Liveaboards
  • Budget Similan Island Liveaboards
  • Last Minute Liveaboard Deals
  • Diving The Similan Islands 2025: A Quick Guide
  • Similan Islands Dive Sites
  • Diving Thailand Guide

Upcoming Similan Liveaboard Availability and Pricing

Check availability and pricing for all Similan Islands liveaboards departing in

    October 2025 | November 2025 | December 2025 | January 2026 | February 2026 | March 2026 | April 2026

(The Similan National Park is closed from mid May to mid October each year)

Similan Liveaboards Trip Reports

Photos from each of the Similan liveaboard trips I've been on over the years.

  • Similan Islands Liveaboard Trip Report 9-13 February 2025
  • Similan Islands Liveaboard Trip Report 21-25 November 2024
  • Similan Islands Liveaboard Trip Report May 2024
  • Similan Islands Liveaboard Trip Report 21 - 25 February 2024
  • Similan Islands Liveaboard Trip Report 15 - 19 February 2024
  • Similan Islands Liveaboard Trip Report December 2023
  • Similan Islands Liveaboard Trip Report October 2023
  • Similan Islands Liveaboard Trip Report April 2023
  • Similan Islands Liveaboard Trip Report February 2023
  • Similan Islands Liveaboard Trip Report December 2022
  • Similan Islands Liveaboard Trip Report February 2020
  • Similan Islands and Myanmar Trip Report March 2015

Crayfish in a rock, Koh Bon
Crayfish in a rock, Koh Bon © chris@divehappy.com

Thanks as ever to the captain and crew of the Blue Dolphin liveaboard again for another great trip.



Diving And Travel Insurance

Considering travel insurance for your trip? World Nomads offers coverage for more than 150 adventure activities including scuba diving, as well as emergency medical, lost luggage, trip cancellation and more.

Start Planning Your Thailand Dive Trip Now!

:: Check the availability and pricing of liveaboards in Thailand and book online.


:: Find the cheapest flights to Thailand - Phuket (airport code: HKT) is the nearest airport for diving the Similan Islands. You can get direct international flights to Phuket or go via one of Bangkok's two airports - Suvarnabhumi (BKK), the main airport, or Don Mueang (DMK), the low cost carrier terminal.


:: Make sure you don't forget to bring any of the essentials for your scuba diving trip with our comprehensive Liveaboard Packing List


:: World Nomads offers simple and flexible travel insurance. Buy at home or while traveling and claim online from anywhere in the world.


:: Find available places to stay in Phuket for before and after your liveaboard on Booking.com - usually you can reserve a room with no upfront payment. Pay when you check out. Free cancellations too.


:: Need inspiration? See our Best Places To Dive In Thailand for ideas of where to go and what to do.


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Last Minute Liveaboard Deals

  • Last Minute Liveaboard Deals May 2025

All Similan Liveaboards

  • Budget Similan Islands Liveaboards 2025
  • Mid-Range Similan Islands Liveaboards 2025
  • Luxury Similan Islands Liveaboards 2025

Similan Liveaboard Reports 2025

  • Diving The Similan Islands 2025: A Quick Guide
  • Similan Liveaboard Trip Report 9-13 February 2025
  • Barracuda Tornado, Koh Tachai, Similan Islands February 2025
  • Manta Ray at Koh Bon, Similan Islands, February 2025
  • Jacks Tornado, Richelieu Rock, February 2025

Similan Liveaboard Reports 2024

  • Barracuda Tornado, Three Threes, Similan Islands, Thailand
  • Similan Islands Liveaboard 21-25 November 2024 Trip Report
  • Similan Islands Liveaboard 6 – 10 May 2024 Trip Report
  • Similan Islands Liveaboard 21 – 25 February 2024
  • Similan Islands Liveaboard 15-19 February 2024

Similan Liveaboard Reports 2023

  • Similan Islands Liveaboard Trip Report December 2023
  • Similan Liveaboard Trip Report October 2023
  • Similan Islands Liveaboard April 2023 Trip Report
  • Similan Islands Liveaboard Trip Report February 2023

Similan Liveaboard Reports 2022

  • Similan Islands Liveaboard Trip Report December 2022
  • Similan Islands Liveaboard February 2020
  • Myanmar And Similan Islands Liveaboard Trip Report March 2015

Similan Islands DIve Sites

  • Similan Islands Dive Sites Overview
  • West Of Eden
  • Shark’s Fin Reef
  • Boulder City
  • Three Trees
  • Christmas Point
  • North Point
  • Hideaway Bay and Tuna Wreck
  • Koh Bon
  • Koh Bon Pinnacle
  • Ao Suthep, Surin Islands
  • Richelieu Rock

More Thailand Diving Stories

  • Thailand Aggressor Relaunches November 2024
  • Blue Dolphin Liveaboard Review
  • Diving Stonehenge, Koh Lipe, April 2022
  • Whale Shark At Hin Daeng April 2021
  • Diving HTMS Chang and Alahambra Rock
  • Thailand’s Best Dive Sites
  • Where To See Manta Rays In Thailand
  • Whale Sharks In Thailand: Where To See Them
  • Are There Great White Sharks In Thailand?
  • Koh Lanta Diving
  • Koh Tao: An Introduction
  • Diving The USS Lagarto Submarine – Richie Kohler interview
  • Cheap Scuba Diving In Asia
  • Thailand Diving Home

Dive Happy Podcast

  • Tonga Humpback Whales Podcast
  • Tubbataha Reef Diving Podcast
  • The Father Of Palau Diving: Francis Toribiong
  • Sogod Bay Diving Podcast
  • LAMAVE Volunteer Whale Shark Research
  • Dream Job: What’s It Like To Be A Marine Biologist?
  • Dumaguete Diving Podcast
  • Komodo Diving Podcast
  • Diving The Yonaguni Monument, Japan Podcast
  • Diving Koh Lanta Podcast
  • Moalboal Diving Podcast
  • Diving The Banda Sea Podcast: Part 2
  • Diving The Banda Sea Podcast: Part 1
  • Diving Hawaii Podcast
  • Diving Malapascua Podcast
  • Diving Taiwan Podcast
  • Diving Japan Podcast
  • Diving HTMS Chang And Alhambra Rock Podcast
  • Diving The WW2 Shipwrecks Of Coron Podcast
  • Diving Lembongan Podcast
  • Diving Romblon: the Philippines’ Secret Super Macro Paradise
  • Triton Bay Diving 2020 Podcast
  • Dream Job: Liveaboard Cruise Director Podcast
  • Diving Triton Bay Podcast
  • Diving Tubbataha Reef Podcast
  • Diving Yap Podcast
  • Diving Truk Lagoon Podcast
  • Diving Sogod Bay Podcast
  • Misool Eco Resort Podcast
  • Diving Palau Podcast
  • The Manta Rays Of Myanmar’s Black Rock Podcast
  • Diving Myanmar Podcast
  • Diving Bali Podcast
  • Diving Cenderawasih Bay Podcast
  • Diving Komodo Podcast
  • Diving Raja Ampat Podcast
  • Dive Happy Podcast Home Page

My Recent Dive Trips

  • November 2024: Similan Islands liveaboard, Thailand
  • October 2024: Forgotten Islands and Banda Sea liveaboard, Indonesia
  • August 2024: Komodo and Saleh Bay liveaboard, Indonesia
  • May 2024: Similan Islands liveaboard, Thailand
  • April 2024: Sogod Bay, Philippines
  • February 2024: Similan Islands liveaboard, Thailand
  • January 2024:Gangga Island Resort, Indonesia
  • December 2023: Similan Islands liveaboard, Thailand
  • Mejangan Island, Bali
  • October 2023: Similan Islands liveaboard, Thailand
  • June 2023: Raja Ampat liveaboard, Indonesia
  • April 2023: Maldives liveaboard
  • April 2023: Similan Islands liveaboard, Thailand
  • February 2023: Similan Islands liveaboard, Thailand
  • December 2022: Raja Ampat liveaboard, Indonesia
  • December 2022: Similan Islands liveaboard, Thailand
  • August 2022: Komodo liveaboard, Indonesia
  • June 2022: USAT Liberty shipwreck, Bali, Indonesia
  • April 2022: Stonehenge, Koh Lipe, Thailand
  • March 2022: Manta Rays at Koh Bon, Thailand
  • January 2022: Richelieu Rock liveaboard, Thailand
  • March 2021: HTMS Chang and Alahambra Rock liveaboard, Thailand
  • February 2020: Similan Islands liveaboard, Thailand
  • December 2019: Raja Ampat liveaboard, Indonesia
  • October 2019: Malapascua, Philippines
  • June 2019: Sogod Bay, Philippines
  • April 2019: Tulamben, Bali
  • December 2018: Sogod Bay, Philippines
  • December 2018: Anilao, Philippines
  • October 2018: Moalboal, Philippines
  • October 2018: Malapascua, Philippines
  • July 2018: Tulamben, Bali
  • May 2018: Raja Ampat, Indonesia
  • April 2018: Sogod Bay, Philippines

My Less Recent Dive Trips

  • May 2017: Apo Island and Dumaguete, Philippines
  • April 2017: Tubbataha Reef, Philippines
  • April 2017: Sogod Bay, Philippines
  • March 2017: Triton Bay, Indonesia
  • March 2017: Raja Ampat, Indonesia
  • September 2016: Tulamben, Bali at Alba Dive Resort
  • August 2016: Cenderawasih Bay on Damai 1
  • April 2016: Sogod Bay at Sogod Bay Scuba Resort
  • February 2016: Raja Ampat and Banda Islands on Damai 1
  • April 2015: Anilao at Crystal Dive Resort
  • March 2015: Myanmar and Similan Islands on Thailand Aggressor
  • May 2013: Similan Islands on Thailand Aggressor
  • April 2013: Tubbataha Reef on Discovery Palawan
  • January 2013: Komodo, Indonesia on MSY Damai
  • August 2012: Cenderawasih Bay, Indonesia
  • April 2012: Similan Islands and Southern Thailand liveaboard
  • January 2012: Similan Islands liveaboard, Thailand
  • August 2011: Hanifaru, Maldives
  • June 2011: Tubbataha Liveaboard Hans Christian Andersen
  • April 2011: Similan Islands and Southern Thailand liveaboard
  • April 2011: Carpe Vita Liveaboard, Maldives
  • March 2011: Lembeh Strait, Indonesia
  • December 2010: Menjangan, Bali
  • July 2010: Tofo, Mozambique
  • July 2010: Sardine Run, South Africa
  • May 2010: Sangalaki / Derawan, Tambora
  • March 2010: MV Flying Seahorse, Similan Islands
  • March 2010: MV Orion, Southern Maldives
  • January 2010: Big Blue Explorer, Palau
  • November 2009: MSY Damai, Banda Sea Liveaboard, Indonesia
  • October 2009: MSY Damai, Komodo Liveaboard, Indonesia
  • October 2009: MV Orion, Maldives Liveaboard
  • September 2009: MV Scubanet, Koh Losin, Thailand
  • May 2009: MSY Seahorse, Banda Sea liveaboard, Indonesia
  • March 2009: Sachika Liveaboard, Maldives
  • February 2009: Daytrips, Koh Lanta, Thailand
  • January 2009: MV Jazz, Burma (Myanmar) Liveaboard

Back In The Day Bragging Rights Dive Trips

  • November 2008: Borneo Explorer, Visayas Liveaboard
  • September 2008: S/Y Siren, Komodo Liveaboard
  • August 2008: Ocean Rover, Sulawesi Liveaboard
  • August 2008: NAD Lembeh Resort, Indonesia
  • June 2008: Koh Tao
  • March 2008: Maldives, Bandos Island
  • February 2008: MSY Seahorse, Raja Ampat Liveaboard
  • January 2008: MV Jazz, Burma Liveaboard
  • October 2007: Bali Dive Safari
  • September 2007: Davao, Philippines
  • July 2007: Great White Sharks, Rodney Fox Liveaboard
  • June 2007: Big Blue, Palau Liveaboard
  • May 2007: Whale Sharks at Exmouth, Australia
  • April 2007: Borneo Explorer, Tubbataha Reef Liveaboard
  • December 2006: Komodo Dancer, Komodo Liveaboard

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  • Diving The Similan Islands 2025: A Quick Guide
  • Similan Liveaboard Trip Report 9-13 February 2025
  • Barracuda Tornado, Koh Tachai, Similan Islands February 2025
  • Manta Ray at Koh Bon, Similan Islands, February 2025
  • Jacks Tornado, Richelieu Rock, February 2025