The Shipwreck Hunter

by David L. Mearns

  Less than half an hour into the turn, with 2,000 metres of cable deployed, all signals and telemetry from the SM-30 towfish were suddenly lost. Seahorse Spirit’s speed was reduced to make some topside checks, but in the end it was decided to recover the depressor weight and towfish to the deck to determine what had caused the fault. As the last metres were being recovered, the lack of tension in the cable could mean only one thing: the depressor and towfish were both gone. The mechanical termination, whose sole function was to securely connect the cable to the depressor weight, had failed. We couldn’t tell what had caused the failure, although a number of strands in the cable were snapped and the strong EAC current was undoubtedly a factor. All we did know was that the towfish was tethered to the depressor weight somewhere on the seabed in about 1,800 metres of water, and that they would play no further role in the search.

  To their great credit, Williamson’s team wasted no time in getting the spare AMS-60 sonar system ready to complete the search. Several attempts were made to acoustically interrogate an emergency system on the SM-30 towfish, but these plaintive pings were met with nothing but silence. It was a very sad end for a legendary sonar: a true workhorse that had located many important shipwrecks, including Kormoran and Sydney. There had been some talk amongst Williamson’s team about the sonar being donated to a museum at the end of this project. Whether that would have happened will never be known. In one sense, the bottom of the ocean may have been the most appropriate place for the SM-30 to end her working life. For millennia, sailors have been traditionally buried at sea. Perhaps it is right that a deep-sea sonar should be afforded the same custom.

  Despite the shocking loss, Williamson’s team had the AMS-60 terminated and ready to be launched later that same day. Ironically, this sonar was better suited for what we were about to attempt. In order to investigate all six targets, a three-legged track-line was created that snaked its way through the search box from north to south. Of the six, only one was close to Rippon’s position. It was a small target with no discernible debris field or acoustic shadow, and looked nothing like the dramatic images that had told me in an instant that we had found Hood, Kormoran, Sydney or numerous other shipwrecks. Even Mike had only picked it out during his second look through the imagery, designating it Contact 09. However, it did show some signs of having hard edges, which was a characteristic we normally associate with man-made objects and not geology.

  The plan was to image all the targets with the sonar set to a 1.5-kilometre swath. We started at 5 p.m. on 18 December and expected the line to take us through to the following morning. There was no point in anyone trying to sleep anyhow, because both sets of thrusters would be going full pelt to counter the EAC, which had ramped up another notch to 4.2 knots. Mike Kelly was in his hut in front of his bank of monitors, ready to analyse each target on the fly, while I was shuttling from the processing system in my hut over to Mike’s to compare notes. Mike liked to work in grey tones, while I preferred a colour scheme that I felt had more sensitivity and was certainly more appealing to the eye. One by one, each target was imaged, assessed and after much discussion discounted as geology, until only one remained: Contact 09.

  This time the target looked more like a wreck, with a clear acoustic shadow and a small cluttering of debris nearby. It was definitely very promising, but it had a strange bend near its middle that required another look. I asked for the second line to be run at a different heading, more or less parallel to the long dimension of the target, that would allow us to accurately measure its length. This produced a better image, with very distinct angularity and shadow, but it still wasn’t definitive.

  I was pretty sure this was the Centaur, but the image wasn’t good enough for me to be 100 per cent certain. The way the project was structured, I had the authority to order the transition to Phase 2, which was intended to confirm the identity of the shipwreck as Centaur by high-resolution side-scan sonar imaging alone. The government had also set in motion the shipping of a 6,000-metre-rated ROV system from America so that it was in Brisbane and ready to be used if the search was successful. A lot was riding on the quality of the image that would allow me to confirm that we had found the wreck, so I was determined to get absolutely the best one possible.

  We had a problem, however. The target was sitting within a narrow gully, approximately 150 metres wide and 100 metres deep, which made obtaining that perfect image extremely difficult. As the Centaur itself was less than twenty metres high, not counting how much the hull had sunk into the muddy seabed, we couldn’t get the image we wanted with the sonar being towed above the gully. We tried that twice with the AMS-60 set at the 1,000-metre swath, and neither image was an improvement on the previous one. In fact they were so poor they were useless. On one of the lines running uphill the towfish nearly collided with the seabed, missing it by only thirty metres. On the second line, the 4.2-knot surface current pushed the Seahorse Spirit so far south we missed the target by nearly 400 metres.

  The only way to get the image I needed was to narrow the swath to 600 metres and tow the sonar downhill through the centre of the gully with the towfish below the top of the walls on either side. I likened the manoeuvre to that scene from the first Star Wars movie where Luke Skywalker has to fly down the equatorial trench, below the deck of the Death Star, in order to fire his proton torpedoes at it. The marine crew running the ship, and Williamson’s team flying the sonar, would have to be inch-perfect to pull this off. On the first attempt the track was too good and the towfish passed directly over the wreck, at nadir, causing the target to be lost in the sonar’s blind spot. At one point the altimeter on the towfish indicated that it got as low as fifteen metres off the bottom, which was much too close for comfort.

  I still didn’t have the image I needed, but if we pushed the envelope too far we risked a collision with either the wreck or the seabed. With the SM-30 sonar already lost, the last thing any of us wanted was to have the AMS-60 join its older cousin on the ocean floor. It was now early morning on 20 December and we had been running high-resolution lines for the past thirty-two hours. Each pass through the gully was a moment of nail-biting anxiety. Was the towfish on line? Was the altitude too low? Would the EAC surge, or drop off suddenly, causing the ship to lurch in one direction or the other? And the worst fear of all: would a critical piece of equipment fail at the crucial moment when the towfish was entering the gully? All we could do was learn from the previous lines we had run and make whatever small changes were possible to reduce the already high level of risk.

  Because the towfish had got too close to the seabed on the previous run, it was briefly recovered to make sure there was no damage. The next line would be our sixth over Contact 09. We had learned that towing downslope produced better images and was safer than upslope, so the towfish was deployed on the western end of the track-line. As the trend of the gully was roughly west to east, the Seahorse Spirit would be crabbing down the line with the full force of the southerly EAC on its broadside. We factored in an especially long run-in to the start of the track-line to give the ship’s drivers enough time to figure out the right heading and speed, as it was their job to effectively drive the towfish down the line. Once the towfish was on track, all that was left was for Williamson’s team to control its altitude with the amount of cable they paid out from the winch. As the track-line was only 1,035 metres long, there was very little scope for corrections once the towfish had entered the gully.

  The final adjustment we made was to shift the track-line from the previous run by twenty metres. If the towfish was where we wanted it, we could expect to see the target on the starboard channel illuminated against the southern wall of the gully. For all the good work that everyone connected with the project had done from the very beginning, it all rested on getting this image to confirm the target’s true identity. By now we were all crammed into Williamson’s hut, where the multitude of sonar and navigation displays would tell us the fate of the project. From the surrounding geology it seeme
d like the towfish was in the right place, but the target had yet to appear. As each second passed the question I asked under my breath was ‘is the target coming, or did we miss it?’

  And then it appeared. A black target about twenty metres to starboard in a zone where the AMS-60 produced its best imagery. Two seconds later, a stark white acoustic shadow appeared behind it. Because the towfish was so low, about seventy metres, the shadow was the dominant feature, which was what I wanted to see. It mimicked the angular contours of the target perfectly. This was no rock ridge: it was a shipwreck. And then came the detail that confirmed the wreck’s identity: a break in the hull at the forward end where I-777’s torpedo had ripped through Centaur’s unarmoured hull. The damage from the resulting explosions was clearly catastrophic, but the bow was still tenuously connected to the rest of the ship. It took the AMS-60 sonar barely eighty-five seconds to show me what I so desperately wanted to tell the government and the relatives: the Centaur was found.

  Before calling Anthony Crack, I took a series of measurements of the wreck to be doubly sure it fitted the dimensions of Centaur. I had been so busy the last few days I had lost track of what day it was, but just as I was about to ring Anthony I noticed it was Sunday morning: a lovely time for him to receive such wonderful news. Anthony had worked very hard to make sure the search had every chance of success, so I was delighted he was the first one to hear. My phone call set in motion a series of formal announcements, the most important of which was an immediate joint statement from Acting Prime Minister Julia Gillard and Anna Bligh that the wreck of AHS Centaur had been located. The news spread very quickly, and within hours messages of congratulations began flooding in to the ship.

  Anna Bligh rang me personally to express her thanks and appreciation to the entire team, which was a very nice touch as I was able to convey her message to everyone on board during our regular midday meeting. While the Williamson crew attempted (unsuccessfully) to locate the lost SM-30 towfish using the AMS-60 system, I was free to write up my last diary for the search. I was especially keen to provide additional information not covered in the official statement, including the position where the wreck was found, lying at a depth of 2,059 metres. It was approximately 1.75 nautical miles away from Gordon Rippon’s dead-reckoning position, and in fact we had detected it on our first search track-line, although this wasn’t immediately obvious. I wrote in my diary that this result was ‘about the best testament you could make to a man whose life was spent navigating the high seas’. For all the doubts about whether he was able to see Point Lookout light, it was important to me that Rippon got the credit he deserved for our discovery, and I was delighted to see that a few newspapers made sure that happened.

  The nice thing about finding the wreck when we did was that the Centaur families didn’t have to spend Christmas worrying about the outcome of the search. They could enjoy the holidays safe in the knowledge that the resting place of their relatives had been located. A message left on the government’s website typified this feeling:

  CONGRATULATIONS. I have just had the only Christmas gift I have ever wanted. I cannot believe this news. I’m just waiting for David’s diary for today to come on the screen. How do I ever thank you amazing guys out there, this is just fantastic. Now I think I’m going to cry.

  My most sincere thanks,

  Sandra Bailey

  Eldest granddaughter of LCPL Charles Richard LeBRUN. My hero.

  The other benefit of finding the wreck before Christmas was that the crews who would be joining the ship for the Phase 3 video and photographic documentation by ROV could return home to spend the holidays with their families. Although the actual search had been completed in less than a week, the work was nonetheless intensive and the break would do people good. I stayed in Brisbane to demobilize the Seahorse Spirit of the Williamson equipment and to ensure that the ROV system arriving from America cleared into Australia without any issues. Phoenix International, an underwater services company started by former colleagues of mine from Eastport and Oceaneering, had been awarded the ROV contract and had sent their 6,000-metre-rated Remora III system out to Australia by sea freight. We had taken a bit of a gamble in sending the ROV system out well in advance of the search, but in the end the timing worked out perfectly. Once the holidays were out of the way mobilization of the Remora III was scheduled to begin on 5 January 2010.

  In the meantime, both the Commonwealth and Queensland governments were able to celebrate our success and their decision to jointly fund the search. I was asked to speak at several press conferences, first with Anna Bligh as soon as the Seahorse Spirit arrived back in Brisbane, and then with Deputy Premier Paul Lucas at the start of the ROV mobilization. The only tricky moment came when I had to explain that confirmation of the wreck as Centaur was based on my interpretation of the sonar images and not on an actual picture. There was a slight rumbling amongst the reporters when one of them pressed me on this question, but my reply seemed to satisfy them as the issue never arose again. Although the imagery wasn’t as clear-cut as it was with either Kormoran or Sydney, the measurements of the wreck and the evident damage perfectly matched what we knew about the Centaur. As no other ship of its size had sunk anywhere near this location, it was inconceivable that the wreck could be anything other than Centaur.

  Press interest in the project was understandably high, especially from the Courier Mail, Brisbane’s main newspaper, which had actively campaigned for the search to happen. Tuck Thompson, the Mail’s lead reporter on the story, was coming up with all sorts of novel angles to make sure that Centaur featured in every edition. He even organized for eighty-seven-year old Martin Pash to travel to Brisbane from his home in Melbourne so that he could congratulate me personally. Martin was one of only three living survivors from Centaur, and I’d made a point of visiting him during the research phase to hear his story. We’d spent hours talking about his life and the effect the sinking had had on him. Despite his humble beginnings as a steward in the merchant marine, he had gone on to do very well for himself in the haulage business and in property investment. He’d lived a good life, taking overseas holidays and buying a new car every two years, and he had the biggest television I had ever seen in a house: a monstrosity that was over a hundred inches wide, which had to be imported specially from Japan. However, when he talked about the Centaur, he would become emotional and cry. The passage of time had not relieved him of the terror he had felt then, and he still suffered from the occasional nightmare.

  The other story the Courier Mail dredged up was whether illegal arms had been secretly loaded on board the Centaur in Sydney, making her a legal target for attack by the enemy. This mystery stemmed from a contemporaneous misunderstanding about the rifles and ammunition carried on board by the 2/12 Field Ambulance crew. The rifles were perfectly legal, but the resulting row led others to speculate that larger quantities of illegal arms were also stowed on board. Unfortunately, these rumours persisted and led others to dream up the idea that Japanese spies had somehow relayed the information to the submarine commander. If this unfounded speculation proved to be true, then it was Australia and not Japan who had violated the Hague Convention rules, an act that had condemned the ship’s company to certain death. Of all the improbable stories about Centaur, this was the one that upset and haunted the relatives the most. Nevertheless, it wasn’t in our brief to investigate every rumour, and either way we had no intention of penetrating Centaur’s hull, given its status as a war grave and protected wreck.

  In fact we had a simple and straightforward objective for the ROV inspection: document the wreck, the damage it had suffered and any associated debris field. Two observers who had taken part in the search – Ed Slaughter, a maritime archaeologist representing the Queensland government; and Major Arthur Dugdale, representing the Australian army — would stay on for the final phase. I was also able to convince Anthony Crack that having John Foley on board would be a huge benefit given his superior knowledge of the ship. Tuck Thompson mad
e a lastditch effort to join us but I vetoed that on the basis that he didn’t have the requisite safety training and we were running out of bunk space. I also didn’t want any outside influences to distract from the job we had to do. Flying an ROV around a deep-water shipwreck can be tense at the best of times, so I didn’t think it was fair on the pilots to add even more pressure to the mix. Tuck wasn’t happy and he predictably criticized Anna Bligh for banning the media, but I had no doubt it was the right decision.

  I wanted everyone’s focus to be on getting the best possible pictures of the shipwreck for the sake of the relatives. Their hopes for the ROV expedition were at the forefront of my mind: in particular their wish for me to make sure a special memorial plaque they had created was laid on the wreck site. I had known about the plaque for months because it was an idea I had discussed with Jan Thomas and Richard Jones at our very first meeting. When I explained how the plaque for HMS Hood was designed to honour every person lost, they adopted the same idea and inscribed a CD with the names of everyone who served on Centaur as well as personal tributes from family members. The memorial plaque was unveiled to the media at the final press conference, held with Wayne Swan, the Treasurer of Australia, whose constituency of Lilley was just across the river from where we were mobilizing the ship. Wayne wanted to wish us well but he also asked me if I had any concerns for the next phase. I did. I was worried about the plaque being lost in the soft muddy seabed because of its weight. It was something I simply would not allow to happen and I needed a plan to make sure it didn’t.