Song Hong Expedition Thailand Nov 2007

By Mathew Partridge

For many years now Thailand has been known worldwide as a haven for scuba divers with its warm tropical waters and multitude of dive sites on both the east and west coasts.

Thousands of divers hit these waters each year in search of whale sharks and manta ray encounters usually with great success. Over the last few years technical diving in Asia has grown with many sites being found and explored around the region.

Dry caving in Thailand has been a popular activity for over a decade by tourists participating in jungle safaris and trekking with some of the most spectacular caves in the world nestled in the Limestone cliffs.

Around 60 million years ago the Indian plate collided with the Eurasian plate causing devastating effects across Asia, forming large mountain ranges like the Himalayas.

At this time lime stone karsts were pushed through the grassy plane to heights soaring well over 100m. Later as the Pacific Ocean began to rise, water began to fill this grassy basin later to be known as the Andaman Sea.

Evidence of these cataclysmic events are still evident today, chains of lime stone karsts and islands like the Phi Phi archipelago span the coastal areas of Thailand.

Over the millennia the rain together with underground fresh water springs have carved caverns and caves above and below the seas surface all over Thailand. As most of these caves were formed before the rise in sea levels, many of these caves are decorated in fantastically shaped stalactites and flow rock. Cave diving in Thailand is pretty much a recent affair with only a few divers possessing the local knowledge, skill and logistics to explore these amazing systems.

One particular Cave had eluded us for several years, the site known locally as the Song Hong Cave, meaning two rooms in Thai.

We had been searching local sources to try and locate the system without joy until October 2007 when on a scouting trip myself and Dr Michael Gadd successfully located and dived the Cave.

We both made relatively simple check out dives to gain an orientation and establish the sites general conditions.

Mike descended to 105m outside the entrance using his Ouroboros Rebreather and I journeyed inside the cave to a maximum depth of 74m using and ISC Megalodon Rebreather. The conditions in the shallows are pretty poor but once below 12m the visibility cleared to around 5-10m and this continues all the way down to the bottom. Water temperature was a tropical 26 degrees inside the cave. Having only traveled with enough gas and logistics for the one dive we would have to return to the site with a full support team and logistics to explore more.

The next month was spent preparing for our November expedition. Extensive logistics in Asia is always a challenge.

Mike and myself joined up with a friend and fellow deep diver Ben Reymenants who would provide a team of medical support from the SSS Chamber network were he works; Ben will be joining us for the deep dives on the next visit.


The expedition was now planned for the 13th to the 17th November. The first few days for myself were spent back in phuket at the Pro-tech facility blending the 11 decompression tanks we would be staging for bailout in the cave and preparing all the logistics and equipment that was needed for a big push dive of this nature. The team then assembled in Krabi, the closest resort to the dive site, a little over two hours away. It was necessary to spend the first day at the dive site setting up our decompression habitat and staging the shallow decompression tanks for the teams push dives early the next morning.

On arriving at the dive site several locals arrived, within minutes of us unloading our pickups over a dozen Thai’s had gathered to see what was going on.

They must have thought the aliens had landed as we unpacked our rebreathers, scooters, decompression habitat and trucks full of dive gear.

Installation of the decompression habit was our first challenge as the rain was hitting us hard and the access area to the lakes edge was muddy and slippery.

Our original idea was to suspend it at 12 meters but as their was no suitable position for this, we had to install it on the ledge directly outside the cave at 16 meters which would mean adjusting the mixes in our large supply tanks to bring the Po2 to something safe to breath.

It proved a challenging affair for our support divers as the rock facedroping from the water edge is littered with extremely sharp rock that could have easily damaged the habitat and put an end to our trip on day one. Once installed the shallow stage tanks, decent line and Buoy were fixed to provide a continuous line with bail gas directly to the surface. Deep divers Mike, Ben and myself were now able to make check out dives and double check that the habitat was installed and usable for the following day. We arrived back that evening to discuss our dive schedules and blend the final gases for our dives, finishing a little past midnight.

An early morning start for the team, a quick breakfast at our resort and it was off to the cave.

Only 5 minutes outside of Krabi and the pickup Ben was driving got hit by a drunken local journeying home from a late night session, half an hour of negotiations a quick video of him admitting it was his fault entirely and we are back on track and heading to the dive site. Upon arrival the locals arrived again in droves right on cue. We got straight down to business, the support team speedily installed the large J-tanks of nitrox needed for decompression and Oxygen incase of emergency at the habitat and we were geared up and ready to go.

The plan was for myself and Mike to dive first as we were both diving rebreathers, me the ISC Megalodon and Mike his Ouroboros with home-build bailout rebreather for redundancy. Ben was diving Open Circuit and diving last as this allowed him the use our bailout gas as additional decompression gas should he need it.

A fast decent past the habitat to the mainline running directly to the cave entrance at 28 meters and in visibility outside the cave was poor but once inside the entrance to the cave at 30 meters it cleared right up to 20 plus.

Mike and I leveled out at 40 meters to check we were ok and all our equipment was functioning and off we went.

Mike had both a primary and redundant Silent Submersion scooters and me my right Primary Leg with bailout left incase of failure. Now deep inside the cave, I had a scheduled dive of 20 minutes in and twenty minutes out to a maximum of 125 meters and mike had a planed 30 minutes scooter in and 30 minutes scooter out to 140m, the aim for him was to concentrate on pushing the cave and laying some new line in the passage way and me surveying the cave. Having swam in for 19 minutes to a maximum of 78 meters it was time for me to turn and head back to my first decompression stop, the cave runs for quite a distance before dropping to depth and is a steady drop off of all the way down. It is only possibly to reach the 100-meter mark with a scooter if not to incur a massive decompression penalty. A slight flow back to the entrance and I arrived safely at my first decompression stop with a reduced hang time of 110 minutes ahead of me. Once back at 30 meters Dr Ljubisa our medical support joined me to ensure all was well and it was. My thoughts were now with Mike and his dive. Having completed my decompression I was keen to find out if Mike was back at the exit and soon after de-kiting it was confirmed he was.

It was now time for Ben to begin his dive as he planned to retrieve the scooters from mike to allow him access to the deep drop off.

Bens planned depth the same as mine. He began his dive and journeyed to 98 meters before turning the dive due to reaching his planned gas reserved and need to head back. Thirty minutes from his decent and it was reported Ben had also safely exited the cave and making his way to the habitat for his remaining decompression.

Six hours had passed and Mike was finishing his final decompression stop, Ben and myself were both back and in good health the support team began to retrieve the stage tanks and scooters all brought back by Ben on his exit and left at the habitat for clearing up later by our support team. Mike finally surfaced with a large grin on his face; he successfully pushed the cave to 141 meters for an impressive 900 meters, the furthest diver to push the cave to date, he achieved his goal of laying new line in the passage way of over 100m a nice way for him to end his birthday.

All the deep divers took plenty of time to rest, hydrate and grab a bite while reminiscing on the trips events, a great trip all around.

We plan to return armed with even more logistics, deeper support, redundant scooters and bailout rebreather to survey the deeper section of the cave` in early spring 2008

I would like to thank the entire team of support divers for all their efforts, Pro-Tech staff for their help with gas blending and logistics and Ismial at Anawin bungalows in Ao Nang for putting up with the team during our visit and One stop dive centre in Krabi for helping us locate the system in October.