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Entry for October 15, 2007

In keeping with the general tempo of this trip, the last day of research was not without drama. The ROV was making its last dive to the deep recesses of the Celebes when ROV operator Toshi sensed a strange drag on the vehicle. His thrusters were whirring, but the vehicle was not responding as it should. The clump weight, which is part of the deep sea ROV system, had become entangled in a line. Becoming tangled in the deep sea is the worst scenario for a manned submersible or an ROV. Stranded submarines entwined in line have been responsible for people's deaths. This happened off the coast of North Carolina with a Johnson Sealink submersible several decades ago. I dived that submarine several years after the tragedy. Many ROVs have been lost when they became entangled. It is very difficult to free a vehicle at depth.

The ROV's dramatic rescue
The line that snagged the MAX ROV was a half-inch thick line, which probably began its life as an anchor line to a long lost fish aggregating device (FAD) and was probably many thousands of feet long. (I mentioned what a FAD is in an earlier entry.) The line was draped over the clump weight, and the ROV was turned to face the problem so that images of the line were transmitted up to us on the ship. The line likely had a very large anchor on one end, and the other end was probably buried in the deep sea sediment. The ROV operates on a 100 foot tether that comes off the clump weight. After a long consultation, it was decided to slowly bring the ROV up to the surface and hope the line would come undone. Instead of what would usually be an hour ascent, it took five hours of slowly raising the system to the surface under the increased strain from fighting the drag of the line and anchor all the way. Once at the surface, Toshi cut cut the line and recovered the vehicle safely. It was a tense moment when he cut the line with a knife attached to the end of a long pole. We had thought the tension on the line would have made it snap dangerously, but it gracefully parted and fell back into the sea. If we could have recovered the line to remove it from the sea, we would have, but it was too firmly attached to the seafloor over 10,000 feet down.

We almost lost the one million dollar ROV that night as the Celebes made one last attempt to keep yet another piece of our deep sea research gear.

The lights are now off in the ROV control room, the last sample jar is sealed, the jellyfish kreisels are disassembled. Mike Cole has stored the RopeCam accoutrements, Nick Loomis and Cabel Davis are taking apart the lasers used to create holographic images of plankton, and we are packing as the last wake of the Presbitero from this expedition forever fades into the deep waters of the Celebes Sea. We have completed our exploration and are on our way back to Manila.

As we cruise again through the Sulu Sea, we are organizing information and just beginning to understand what we have learned. It will take months, even years, to process the samples and analyze all the images and video. We all feel privileged to have been able to explore the deep ocean at the very center of marine biological diversity.