Note: Following is another chapter in the unfinished (and likely never to be finished) companion book to our recent IMAX film, Deep Sea 3D. The story is about filming Sand Tigers with Olympus Divers. We had so much fun that a group of us returned for another four days of diving last month (October 2006).

Chapter 18 – Sand Tigers
June 9, 2005
Moorhead City, North Carolina

George Purifoy concentrated on the fathometer as the GPS navigation system guided us closer to our dive site. We were more than thirty miles offshore from Morehead City, North Carolina and land was far too distant for visual navigation sightings. But the GPS system was extraordinarily accurate and soon a jagged tracing on the fathometer revealed the location of the shipwreck Papoose. George yelled, “Go!”

Bobby Purifoy, encumbered with massive double tanks, wearing a full-face mask, and cradling the M/V Olympus’s anchor with twenty feet of heavy chain draped over his arm, released his grip and leapt off the bow. In a cloud of exhaust bubbles, Bobby plunged one hundred and twenty feet straight down. He landed heavily on the sandy bottom very near the upside-down wreck and quickly wrapped the anchor chain around a splinter of torn metal where the ship’s spine had broken after a German torpedo exploded against her hull during the second world war. George had developed this dramatic anchoring system to insure the dive boat was securely anchored on the wreck before the boat drifted away from the site and his boat-load of technical divers descended over one hundred feet only to find an empty plain of sand. Bobby’s full-face mask allowed him to transmit a pre-dive report to George via the OTS underwater communications system. After a long five minutes Bobby transmitted his report.

“We’re tied in at mid-ship. Visibility is about seventy feet and we have a mild current running toward the stern. “I’m seeing lots of sharks. I saw more than a dozen on the way down.”

Twenty minutes later I dropped off the swim step, descended fifteen feet and began swimming toward the bow of the Olympus. George, Stuart McFarlane, and Dylan Reade had already swung the heavy IMAX 3D camera over the side and lowered it to Dave Forsyth and Richard Herrmann. Now I could see Richard’s and Dave’s exhaust bubbles rising beside the anchor line that disappeared into the dark grey water below. I checked my rebreather instruments, deflated the air in my buoyancy compensator and allowed myself to fall. Clouds of gelatinous ctenophores and siphonophores drifted past as I fell and two large silvery African pompanos rose to check me out.

Water visibility was hardly crystal clear, but it was plenty good enough for our purposes. We had come to North Carolina to film sand tiger sharks. These are six- to ten-foot long sharks that are characterized by spectacular fangs protruding menacingly from the sharks’ upper and lower jaws. We wouldn’t need great visibility because the IMAX 3D shots I had planned would only work if the camera lens was within four feet of a shark’s face.

In addition to this species of shark’s impressive dentition, there were two other facets of their natural history that made them interesting. Unlike most sharks, the sand tigers are capable of maintaining neutral buoyancy. Sharks don’t have swim bladders for neutralizing buoyancy like bony fish. So most sharks either rest on the bottom when not swimming or must swim all the time to prevent sinking. Sand tigers, however, have eliminated their buoyancy problems by swimming to the surface and gulping enough air to allow them to be neutrally buoyant at depth. How they manage to swim down over one hundred feet after gulping that much air is a mystery to me, but the behavior has been well documented. I had no hope of filming sand tigers as they swam to the surface to gulp air. That shot would be difficult enough with a small video camera. With the IMAX 3D system it would be essentially impossible. I did hope to film a shark hovering motionlessly over the bottom. This would justify our narrator mentioning the sand tiger shark’s unique behavior.

The other aspect of sand tiger natural history was much more interesting and it was the primary reason we came to North Carolina. The ocean floor off Morehead City and Cape Hatteras is a flat sandy plain covering hundreds of square miles. There is almost no shelter for smaller fish species except the hundreds of shipwrecks that litter the ocean floor, most of which were merchant marine victims of German U-boats during the war. Enormous schools of small fish swarm through the ruptured hulls of these wrecks, dashing inside the wreckage as schools of large predators like jacks or barracuda rush in to attack. Without the shelter provided by the wrecks, these small fish would be quickly consumed by predators.

There is one other extremely unlikely place these schools of small fish can find refuge besides the shipwrecks. They find refuge around sand tiger sharks. These small fish are too small to be of much interest to the sharks. Larger predators like the jacks and barracuda, however, would be welcome prey for the sharks. So when the schools of small fish cluster tightly around the awesome jaws of the sand tigers, jacks, barracuda and other mid-sized predators are hesitant to attack. It’s an interesting example of symbiosis. And it is also spectacularly beautiful. I was sure that 3D images of these large sharks surrounded by a dense lion’s main of tiny silvery fish would be absolutely stunning.

After reaching the bottom I checked my instruments once more to make sure my rebreather electronics were working properly and that my oxygen pressure was set at one atmosphere. Then I unclipped the light meter that was attached to the side of the camera and turned it on. Bob Cranston, Peter Kragh and Mark Thurlow arrived at the bottom moments later and began attaching the four 650-watt movie lights to the mounting bracket on the camera. When they were done I helped Bob adjust the lamp heads and then waved Richard and Dave away. They would return to the boat and wait for us to call them back for camera retrieval. By that time Bob, Peter, Mark, and I would probably be committed to more than two hours of decompression. Hanging on the anchor line for hours while trying to control the massive camera would be difficult at best. So I had devised this system of using an open circuit launch and recovery team to deliver and return gear to the boat, including the IMAX 3D camera.

I keyed my microphone and spoke to the other rebreather divers. “Okay, let’s move toward the stern. Mark and Peter, keep and eye out for sharks and let us know if any are approaching.” Swimming with the large camera is not only cumbersome and slow, but it is also visually debilitating. With the huge metal housing next to you and the bright lights in front, it’s difficult to see much of what’s going on around you. I can’t even see Bob who is on the other side of the housing helping me move the camera through the water. The housing is so big it occludes his whole body. When I want to change directions I let him know via the underwater comm. Otherwise we end up fighting each other to control the camera’s direction of movement.

“Shark coming toward you near the bottom along the side of the wreck,” Mark called.

“Okay, okay,” I replied. Then I let go of the camera and rose up a few feet to see past the bright lights. The shark was about fifty feet away and almost motionless. Its neutrally buoyant body was drifting slowly in our direction surrounded by a beautiful cloud of silvery fish. “Okay, I see it. Bob, let’s move in very slowly. I’m powering up the camera now.” I turned the power switch to “on” and pre-adjusted the focus to five feet.

“I get f-11,” Bob said.

“Okay, okay. F-11,” I confirmed as I adjusted the aperture setting. We were all set. I looked over the camera again to check the location of the shark.

“Okay, let’s frame him up,” I said letting Bob know he needed to find the shark in the video viewfinder and place the image just below the centerline crosshairs.

One of the problems with doing wildlife film work in IMAX 3D is that you must anticipate what an animal is going to do so that the scene begins before the action takes place. Then you must add five seconds to that because it takes that long for the camera to ramp-up to full running speed. It’s really easy to guess wrong and often the scene never develops. With the sand tigers this most often happened because the shark simply changes direction. When the scene fails to develop it’s painful because the cost of shooting the film is about $60/second. And with a maximum running time of seven minutes, the failed scene leaves you with that much less film in the camera. At a depth of 120 feet our dive would last over four hours leaving us only time to make one dive per day.

When the shark was twenty feet away I triggered the run switch. Then as the camera was accelerating the film to full speed I pressed my mic button and yelled, “Camera running.” Then Bob and I struggled to move the camera forward while at the same time holding the image of the sand tiger steady just below the cross hairs in the viewfinder. Maintaining good composition in the viewfinder requires a great deal of effort from both Bob and me. Seen from behind, the camera often disappears in a cloud of murk as Bob’s and my fins beat the water furiously to guide the huge camera steadily in the right direction. This spasmodic flailing of fins combined with grunting and the more than occasional expletive yelled into the mouthpieces of our rebreathers often results in surprisingly steady images.

The image of the sand tiger grew steadily in the viewfinder. Then when it was about seven feet away, the shark turned revealing a huge cloud of silvery minnows clustered around its flanks. “Let it go,” I yelled letting Bob know that I wanted to hold the camera steady as the shark swims out of frame.

“That was good,” Bob said after I switched the camera off.

“Yeah, not bad, not bad,“ I said.

“There’s sharks to your right, under the wreck,” Thurlow reported. I turned to my right but didn’t see any sharks and wasn’t sure what Mark was talking about. “Under the wreck,” Mark called and as I turned to look at him he pointed into a dark area at the base of the wreck.

“You’ve got the camera,” I told Bob. Then I swam over to the wreck and looked into the dark hole. There were three sand tigers hovering inside. “Bob, come here and take a look,” I said. Bob passed the camera off to Peter Kragh and moved over to look into the dark hole. Two of the sharks had already left via another opening and as Bob looked inside the third shark was also leaving.

“I think we could get the camera in there,” Bob said.

“Yeah, that’s what I was thinking.”

I checked my decompression computer and noted that I already had more than forty-five minutes of decompression ahead of me. Oh, well, I thought. That’s the beauty of our Mark 155 rebreathers. We can stay underwater as long as it takes – up to twelve hours if necessary, although a dive that long was well beyond my physical endurance ability.

Bobby Purifoy had brought down a few fish scrapes in a plastic bag for bait and had hidden the bag under a plate of metal a few yards away. As Bob and I struggled to maneuver the camera into the wreck, Mark swam off to get the bait. Once we were deep inside the wreck we turned the camera around and pointed the twin 3D lenses out toward the opening. The image in the viewfinder was now the opening fissure surrounded by jagged metal. “That’s the shot,” I said pressing my mic button.

“Looks good,” Bob responded. “The light cables are in the shot.”

“Peter, bring the lights in from the other side,” I said.

“Okay, okay,” Peter responded.

Bob and I then removed the lights from the camera and passed them to Peter. He would find a back entrance into the wreck and thread the light cables in from behind so that the cables would not be in our shot. While Peter searched for the best way to bring the lights to us from behind, Mark returned with the bait. I moved around to the front of the camera and pointed to several spots where I wanted Mark to hide the bait.

“Stick some there and there,” I said pointing to spots where the bait could be hidden under the wreckage. “Push it way in so the sharks can’t get it.” As Mark was deploying the bait, Peter passed Bob the lights and I helped him mount them back onto the camera. With the light now illuminating the wreckage around the opening, the image in the viewfinder really looked great. Once the lights were on the camera I looked up to see Mark rubbing bait on the metal a few feet from the camera.

“Here they come,” Peter said. I looked out the opening but couldn’t see any sharks yet, but I knew Peter was saying that sharks he could see had begun to respond to the bait.

“Okay, Mark,” I said. “Get out of here!” If our plan was successful, it was going to get very crowded inside the wreck and Mark had the scent of bait on his hands. Mark didn’t bother to respond. He rubbed his hands together vigorously as he swam quickly out the opening and up over the wreckage where Bob and I had wedged ourselves with the massive camera. Then we waited.

It felt a bit like we were entombed inside the wreckage. I was wedged between the jagged wreckage and the big camera in a very awkward position. I moved my left hand down to check my VR3 decompression computer and, because I was jammed up next to the wreck, struggled to find it. When I got it out and looked at the LCD face it was too dark to read it. I struggled a bit more to press the light button and a moment later the LCD screen lit up. The display indicated our depth at 124 feet and my decompression obligation was now one hour and fifteen minutes. I didn’t bother to notice how long we had been down. That was irrelevant at this point. What mattered was how long we would have to decompress if we ended the dive now. I looked back up to the viewfinder and waited.

There was very little current carrying the scent of bait out of the wreckage and it took about fifteen minutes for the sharks to figure out where the odor was coming from. Occasionally a shark passed across the opening and I was tempted to take a shot, but I wanted two or more sharks inside the wreck with us well lit by our bright movie lights.

“Let’s wait for it,” Bob said.

“Yeah, we need them in here with us. It’ll happen. Let’s wait,” I agreed. We waited.

I began to notice pain in my side and back. I tried to move and change positions, but there wasn’t much room. The pain increased quickly and alarmingly. A shark swam into the opening then turned around and left immediately. I considered pressing the run switch, but with the camera’s five-second ramp-up time, the shark would have been gone before the film was recording an image. As we continued to wait, the pain in my back and side continued to grow. Soon it hurt to breathe.

“I’ve got some pain in my side,” I said pressing my mic button. “It’s pretty bad and I don’t know what’s causing it.” I wanted Bob, Mark, and Peter to know I was having pain in case the pain persisted on the surface later. If the pain originated on the bottom, it couldn’t be decompression sickness. If I didn’t mention it now and then reached the surface complaining of serious pain, everyone would assume I was bent, no matter what I said. I wanted them all to know that decompression sickness was not a possible cause. What was causing the pain, however, was a mystery. Soon every breath caused searing pain in my back and side. I continued to try moving, straightening my back and left leg, but the position was too cramped. Moving the camera would mean losing the composition we had carefully created. I reached down and checked my computer again. The light came on the screen showing over two hours of decompression. I realized that whatever was happening to me might make enduring over two hours of decompression very difficult.

“Two sharks heading for the opening,” Peter reported. As soon as I saw one of the sharks enter the opening I pressed the run switch. The shark swam into the camera’s movie lights then turned and swam back toward the opening, but before I turned the camera off I saw another two sharks approaching. Both swam into the wreck followed by a third. One of the sand tigers swam beneath the camera and began thrashing around next to my right leg. Instinctively I wanted to pull my leg up, but there was no room and at the same time the image in the viewfinder was getting better and better. In addition to the shark searching for the bait beneath the camera and next to Bob’s and my legs, four other sharks had swam into the wreck and their spectacular fangs shinned under our powerful lights. Neither Bob nor I said anything. We were too intent on holding the camera still as the shark near our legs thrashed around. I was torn between concentrating on maintaining composition, worrying about the shark ripping into my right leg, and the pain in my side, which had become so intense I began to worry about my ability to keep breathing.

All of the sharks left the wreck after about ninety seconds. I let the camera run for another thirty seconds allowing the last of the film to run through the magazines. The film load ended with a satisfying “thunk.” In agony, I pushed myself past the camera and clawed my way out of the wreck. “Recover all gear,” I gasped through my rebreather mouthpiece.

“Surface copy,” Mark called.

“Surface copy,” Michele responded from the Olympus.

“Recover all gear,” Mark repeated.

“Surface copies, recover all gear. Recovery crew on the way,” Michele responded.

Outside the wreck, holding on to a rusty splinter of wreckage, I stretched by back and side. I injected air into my dry suit and raised my left leg allowing the gas to relieve the suit-squeeze that had gripped my left leg for so long while I was inside the wreck. Almost immediately the pain began to subside. I slipped my fins on, which I had left wedged under the wreck before entering the opening an hour earlier. Then I swam up to the keel of the Papoose where our anchor was tied in. By the time I reached the anchor line the pain was gone. I checked my decompression computer. I had two and a half hours of decompression starting with an 82-foot deep-stop. I was so relieved that the pain had disappeared I didn’t care a bit about the long decompression I was facing. Without that mysterious pain, I could do two and a half hours standing on my head!

At sixty feet I pulled out my jon-line and looped it around the anchor line. Then I clipped the line to my buoyancy compensator, relaxed and closed my eyes. We had done well, I thought to myself. “That shot will be in the film,” I said keying my mic without addressing anyone in particular.

“Yep,” Bob responded. “It’s in the film.”

Two and a half hours later Bob, Peter, Mark, and I reached the surface. While we were decompressing Michele made two dives with her still camera along with other members of the launch and recovery crew and boat crew. Each time Michele disappeared into the grey water following the anchor line down to the wreck I checked my watch then waited anxiously for her to reappear thirty minutes later. We had left bait hidden in the wreck and I couldn’t help being concerned as she descended toward a wreck 120 feet below the surface surrounded by agitated sharks. But each time she came back up the anchor line and proudly replayed for me digital photos of fang-filled shark faces photographed from two or three feet away.

I have never determined the cause of the pain I suffered inside the wreck of the Papoose. It was probably one of two things. Either I had a muscle spasm that, in those cramped quarters, I couldn’t relieve. Or, perhaps more likely, the suit-squeeze on my left leg and especially my femoral artery had reduced circulation so dramatically that the suffering nerve tissue began to rebel. Once outside the wreck and able to move, however, the circulation was restored and the pain abated. Of course, these are only guesses. I probably never know the cause for sure.