Reliable power for extreme settings: bebob Vmicros support National Geographic's Thai Cave Rescue docu

In the summer of 2018, the whole world held its breath when a young football team and their coach were trapped in a Thai cave, Tham Luang Nang Non, by a sudden flood. Their chances of survival seemed very slim due to the complicated local conditions - but after nine days, divers actually managed to rescue the boys and their coach.

plakatA few months later, work began on an ambitious film project led by Mallinson Sadler Productions. For the National Geographic series "Drain the Oceans" a documentary of the rescue was to be shot, together with a 3D laser scan survey of the cave.

Please read GBCT Director of Photography Rob Franklin's breathtaking and touching story for yourself (photographs by Mark Burkey):

It’s June 2018, 10.30 in the morning and I’m just about to take my seat on a flight to Liberia for a BBC shoot and the phone is ringing. It’s a caving friend with an urgent request for diving equipment, “is it for Thailand?” I ask “Yes” comes the response.  “Ok, Here’s what I’m going to do” I reply ”I’m on a flight, the doors are closing I’m going to send a text to home but just take what you need”.

A few days earlier there had been a report on the news that flooding in a Thai cave, Tham Luang Nang Non, had trapped a young football team and their coach and their chances of survival seemed remote.

Now an international rescue operation was underway, spearheaded by friends and members of the Cave Diving Group (CDG) and British Cave Rescue Council (BCRC)

We are now all familiar with the rescue, 12 boys and their coach found alive after nine days by divers John Volanthan and Rick Stanton in a remote part of the cave beyond hundreds of meters of flooded passages.

The tragic death of the former Thai Navy Seal Saman Kunan whilst installing diving cylinders into the cave highlighted the real risk to all those involved.

The early arrival of Monsoon rains with even more rain forecast and a window of opportunity to rescue the boys that was closing. All elements of an extraordinary disaster movie but this was real life and what unfolded was an audacious and unique plan with an extraordinary ending.

In Liberia, the crew, virtually all the hotel staff and I were glued to the evening TV news reports. Over the next few days news of boy after boy being brought out alive was greeted with cheers.

It seemed for a moment the world was united and that under the spotlight of the worlds press something truly amazing had been achieved in a multi-national effort that eclipsed even the story of the trapped Chilean Miners that happened some years previously.

Fast forward a few months and I get a call from Sophie Elwin Harris, a director I have worked with before on the Greenland Ice-cap. She had recalled I was a cave-diver, caver and had previously filmed extensively in caves for the BBC and National Geographic. “Would you be interested in making a documentary about the Thai cave rescue?” “I would most definitely” I replied, “quite a few friends and some of my kit was involved”.

Sophie was working as a Producer/Director for Mallinson Sadler Productions in Bristol for the National Geographic series “Drain the Oceans” and now a Thai Cave Rescue version of the series had been given a tentative green-light.

It was an ambitious idea.  A 3D laser scan survey, comprising of billions of data points of the passages would be used to build a virtual image of the cave and the surrounding mountains, to show how and why the cave flooded so rapidly.  Richard (Roo) Walters a caver and surveyor from Commendium Ltd was called in. Roo and his team had previously surveyed caves using this technique before. Combined with archive of the actual rescue and new documentary work from us inside and outside of the cave it would be a powerful film.

The Thai authorities however were anxious that more curious visitors would become stranded so the cave entrance had been fenced off and nobody was allowed in, especially the media.

It seemed impossible to get inside the cave to film or survey and what followed was months of patient negotiations led by Sophie, our fixers in Thailand and the local cavers who had been involved in the rescue, Vern Unsworth and Josh Morris. Josh in particular played a key role with his expert translation and knowledge of the Thai way to do things when it came to negotiating. Vern had made hundreds of explorations into the cave so his knowledge of it was second to none.

Sophie had been caving once at University and hadn’t particularly enjoyed the experience, so to bring her up to speed and comfort I took her caving in the Mendips. It was a typical February day, low cloud hung across the hills and a chill wind drove the rain toward us but at least it would be warmer underground. It was nothing too serious, an easy cave with a few climbs, a few crawls and a bit of chilly water but enough to see how she handled being underground. She described it as being challenging and unpleasant, wet and claustrophobic. Thailand would be warmer and drier I told her, I’m not entirely sure she felt reassured.

It took months of negotiations but finally permissions were all in place and the shoot and the survey were finally green lit. The production office team had been amazing, Rich Hyland our Production Co-ordinator had attended to every last detail and finally all of the permissions fell into place. Boarding the British Airways Flight to Bangkok I couldn’t help reflect that 10 months before this was the journey that friends had made with their cave diving kit on their way to a rescue that had seemed hopeless.

A warm welcome greeted us in Thailand, Roo Walters and the survey team had arrived a few days earlier.  Rob Harper a British caver who had been on the original rescue now on holiday with his wife and Vern Unsworth a member of the same caving club as myself but now living in Thailand. Vern in particular had played a key role in the rescue and had probably explored Tham Luang cave more times than anyone previously. Together they would be contributors to the film and vital help whilst filming underground. It was also time to be reunited with Nop our Thai Gaffer who I had worked with before.  What he lacked in caving experience he more than made up for it with boundless enthusiasm and a mile-wide smile. Our lack of a common spoken language often left us both giggling as I tried to pronounce the Thai phrase for “spot it up”.

Now we had just a few hours to check the camera kit, prep everything for cave travel and rest before our first visit into the cave.


Important kit choices

Sorting the kit into loads for the caving tackle bags I was pleased with some of the decisions I had made a few weeks earlier. We were shooting on a mixture of Sony FS7, Red Dragon and Osmo Gimbal. Both cameras I had stripped back to the bare essentials to make them as light as possible and easily transportable in the cave. Working over 4Km and over three hours from the entrance we were entirely reliant on battery power, camera, lights and sound with no possibility of either charging or sending a runner to get anything we didn’t have. Having tested all the new options for mini Vlock batteries I settled on the new bebob 150micro series. They have very consistent duration and current draw with a robust and compact construction. I have a special waterproof pot normally reserved for camera batteries, well battery actually as just one conventional Vlock will fit in it. Now with the bebob I could fit three in the same container. It later transpired that with careful power management 1½ batteries would last a full day of filming underground.

Cooke S4 primes and Angenieux zoom’s were chosen for the lenses, together with Tiffen IR/ND/Pola combination filters for outside the cave. I had used Cooke lenses previously on many shoots and apart from their unique look their lightweight and compact size was appealing.  My faithful Sachtler tripod was stripped of all un-necessary weight as I have previously done for high mountains in Alaska and the Himalayas.

Most Broadcast Film and TV lighting isn’t very good in caves, its usually too fragile and doesn’t have enough “Oooomph” for big passages. Instead I have custom built lights some with 200Watt LED dimmable outputs some much smaller. There is one tiny exception, I have an Aladdin Eyelight Bi colour which was a present from a Gaffer I work with a lot in London. That goes with me almost everywhere and its great for those tricky to light close ups or indeed as an eyelight.

Then with loving care every piece of kit was packed in grit and moisture resistant bags wrapped in foam matting and placed in the caving tackle bags marked carefully with the contents. Once in the cave all the bags will most likely look the same, dirty dusty and a bit battered. Locating the right piece of kit underground could quickly become a nightmare without meticulous preparation.

In the early morning light the distant shape of the mountains looks like the outline of a sleeping woman on her side. In Thai folklore this is a Princess who was not allowed to marry her soldier love so she killed herself.  Tham Luang Nang Non is translated as Great Cave of the Sleeping Lady, at the cave entrance there is a shrine to her and all that visit or venture in. We too paid our respects and lay an offering of flowers. It not the largest cave I have ever been in but by UK standards its huge. Swifts spiral around the lush vegetated rock and the entrance is bisected by the iconic rusting safety rail against which the boys propped their bikes as they set off to explore. A long mud slope leads down to broad passages and now with everything bone dry its difficult to imagine a raging river flowing out of it but that’s how it would have been during the rescue. We are filming at the end of the dry season, all water has now gone from the cave and where will walk the divers had to swim.

Soon the heat of the early morning sun and the soft light of the entrance disappeared and we are enveloped in the velvety blackness of the cave. Tham Luang is mostly shades of mud brown, dark mud, light mud, sandy mud, gravelly mud it’s all the kind of mud that pervades everything and kills camera equipment. Our lights cast odd shadows on the rock as the trail starts to become harder to discern.

Quite soon we are at the chamber where a Tyrolean traverse is still in place after the rescue, the plastic stretcher sled still hanging from the pulleys. This aerial rope way was used to speed the boys over a large void which we now had to climb around the edge of, hopping from mud covered slippery boulder to the next, climbing up and down. Delicate and time-consuming for us, the boys would have moved faster strapped into a stretcher and guided down the ropes by the rescue team.

Shortly after we clamber down through tangled jammed boulders to the start of the passages that had been completely flooded during the rescue. The line used as a guide by the divers is still in place and apart from an initial low section the passage was straight and spacious. Further and further into the mountain we travel and making good progress. Our destination is the chamber where the boys had sat for nine days before being found by the divers John and Rick.

Some of them would spend another nine days waiting for their turn to be rescued. 

Along the way we pass several pinch points where the diving line threaded between stalactites hanging from the ceiling caused problems for the divers transporting the boys out of the cave. We could now see what the divers couldn’t during the rescue. The cave was quite wide and the guide line had been laid in the highest part of the passage so that all possible airspaces near the roof could be searched just in case the boys had found refuge.  That line was some 4m above us amongst the stalactites. It was clear to us how difficult the rescue would have been with just the guideline and the sense of touch in the zero underwater visibility negotiating a slot just 500mm wide.

A line trap follows shortly after. The cave passage is wide and slanting, a lozenge shape where the top corner narrows to a crevice of just a few inches. The diving line at this point is under tension and so when pulled downwards the diver can follow it with relative ease. If the line is accidently let go of then it disappears out of reach into the crevice effectively “trapping” the diver with a loss of direction and guidance. Chris, one of the divers had this happen on the final day of the rescue when transporting one of the boys. He spent an anxious few minutes searching for the line before finding a cable, following this led him with some relief back into a known chamber, slightly shaken but undeterred.

Sam Yek junction follows, 1.5km in. Its here as the survey would later reveal that the water trapped the boys. Sam Yek is the meeting point of two streams, the main stream, which floods relatively slowly, and the stream from Monks Series, which responds to water from the surface much more quickly. The junction itself is a shallow depression with a mud pool which ponds the water, which then starts to back up the gently upwards-sloping passages on either side forming a sump. Vern tells me it’s the point he reached on the day the boys were first missing. Just a couple of days later the water was around 2m deeper which would have meant substantial flooding of the near level passages on either side.

We stop to rest and the team is in good spirits. In the darkness of the cave jet lag doesn’t seem to be a factor just yet. Sophie, the director, seems to be enjoying the cave far more than our last underground adventure in the Mendips and it is warmer too. In fact it a lot warmer, no full-length fleece suits and waterproof over-suits here, thin trousers and a light thermal top is all that’s needed. When moving in the cave even this is sometimes too much and with 100 percent humidity we are all drip with perspiration in an instant. Nop, our gaffer, was still smiling too.

Further on the passage changes shape and size and becomes a low crawl way filled with soft sand to within 40cm of the roof. To make it worse the way through zigzags around pendants of rock hanging from the roof. A strong draught guides you through but the low passages push your face into the sand. It’s a test for any caver. Clipping my bag, containing the camera to a short towline I launch myself into the crawl loose particles of sand blowing into my eyes.

Once through I ditch the bag, then partly insert myself back into the crawl to set up a small camera but more importantly to be a friendly welcome face for Sophie whom I know is dreading this part of the cave. The survey team have buoyed her spirits and have told her to recite a nursery rhyme repeatedly and not to stop. In a few minutes I see her face coming out of the darkness Her eyes tell a story of part terror and part relief, she is so happy to have made it through. I’m overwhelmed with her courage and professionalism.

On the far side of the crawl we continue into the cave, the diving line still our constant companion, an hour or so later the dive line suddenly stops. To the left is a dark brown mud slope and to the right is a steeper slope with the dive line tied to a plastic tube pushed into the mud. We are suddenly here, chamber nine the place where the boys were stranded. A dark space soars almost out of sight above us.

Everyone is humbled, over 4.5km from the entrance and with 600m of limestone over our heads it’s taken us over 3 hours with the film kit to get here. We had all thought we knew the story of the rescue and what it had taken to get the boys out, but we had travelled in the dry, no flooded passages, no lakes or canal’s. Now we are here the enormity of the rescue and the reality of it begins to sink in.

Our first sequence to shoot is the survey team arriving at Chamber 9 – the place where the boys spent their eighteen days, forced to climb further and further up the mud bank by the rising water.  As we start to climb up the steep mud slope we see around us are the discarded foil blankets, plastic spoons, torches and medication packets that the Cave divers and Thai Navy seals brought in for the boys. Shallow depressions in the sand with a small rounded pile like a flattened sand castle mark where the boys had slept. On a mud-covered rock the Thai Navy seals have carved their emblem at what is now a shrine to survival.

Sophie and I discuss the sequence. We had discussed it many times before over a coffee in the warmth of the Bristol Production office, then it was in our imaginations now sat here hot and sweaty covered in grime we could really begin to shape what we wanted to do. I scampered back down the slope to chat to Nop and Vern about lighting then to Rob about sound. Rob Myler was our assistant producer, researcher, time-lapse genius, DiT and sound recordist. A talented addition to the team, he did everyone of those jobs expertly whilst at all times being quietly good humoured and confident.

Filming in caves is always problematic, it’s dusty, dirty and there is no ambient light. You have to meticulous, laying out a clean mat or towel, then after cleaning hands open the bags carefully before taking the kit out for use. Turn off your helmet lamp and in instant velvet darkness descends. I find it comforting but I’m not sure why, others find it stygian, uncomfortable, foreboding and no matter how long you wait your eyes will never see though the blackness. This means every shot needs to be lit in some way that feels natural to the eye and camera but isn’t just reliant on the cavers helmet lights. A choreography of carefully coordinated lights follows. Nop, Vern and other members of the team, hidden out of sight, hold the lamp heads. On “action” the lights dance around the frame, coming and going as the cavers climb the slope for the first time. Roo who heads up the survey team starts to look around and Sophie pitches a few questions to him. Roo, like so many others in the cave including myself know some of the British cave divers personally and count them amongst our friends. He sums up in a few words what everyone feels and his answers begin to falter with emotion.

 Shot by shot we work through the sequence. We film the survey team set up the laser scanner to record the first of over eight billion data points that will build the virtual cave. Later we shoot cutaways. One is particularly poignant, plastic spoons pushed handle first into the sand on little ledges, each one representing a boy.

In a cave you have no sense of time, sometimes you can be tired and in the outside world its still late morning or you are wide-awake and outside its 03.00 in the morning. I deliberately don’t wear a watch and when resting sitting in the dark to conserve the light power that will show the way out and eating and drinking only when hungry or thirsty

In one of these resting moments, all lights are off and in the darkness Sophie and I discuss the shots so far, we have been at Chamber 9 for 8 hours and it’s getting late. We are all physically and mentally tired and we still have the long journey back to the entrance to do.

“Ok everyone,” says Sophie “that’s a wrap for today” everyone is quiet but out of the darkness there comes a quiet “yee-ha”, we all burst into laughter. It’s the first day of several long days in the cave and Nop our gaffer is more than pleased, it seems, to be returning to the daylight.

Gear packed for travel we start the long slog back to the entrance.  Thoughts turn to a shower, food and cleaning the kit for tomorrow where its going to be another long day.

 I have had some amazing experiences in my career but Tham Luang was one of the most interesting. Seldom, if ever, is there the opportunity to work with friends as contributors. Rarely is there the opportunity to visit a place such as Tham Luang cave and understand first hand how a rescue like this unfolded. Would I do it again? In a heartbeat.

It was an unprecedented event, in all over 10,000 people from 20 countries with over 100 divers took part. The boys survived their experience and the rescue will be remembered for many years to come.

Fact File

Drain the Oceans, Thai Cave Rescue airs on the 6th January 2020 on National Geographic at 20.00.

© Rob Franklin 2019 2020

Rob Franklin GBCT is a British DoP who has a passion for caving and cave diving and who has often been fortunate to combine this with his professional life. Starting at the BBC his career has spanned over 30 years and he now specialises in underwater filming for commercials, drama’s and feature films.

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