Dr. Richard Pyle
Our drop-point was an undersea pinnacle known as Mount Everest. Howard and I would cling to the…

This field report first appeared on the NY Times Green blog December 30, 2011 as part four in a six-part series.

DeepSee hovers nearby as I prepare to send the anchor line to the surface. Photo: Howard Hall.

Some days ago here, in a rich biodiverse ecosystem off the Costa Rican coast, we had planned to take another step closer to my lifelong dream of fully integrating advanced closed-circuit rebreather technology with a sophisticated submersible to leverage the strengths of each for exploring the coral reef “twilight zone” — that is, coral-reef habitat at depths of about 200 to 500 feet.

Unfortunately, the current was too strong, so the film producer Howard Hall and I made a shallow rebreather dive a few days later to observe sharks and other large animals off Cocos Island. But a few days later, we tried the deeper dive again, and succeeded.

While the crew of the Argo, our home vessel, prepared the submersible Deep See for its morning launch, Howard and I assembled our rebreathers and got ready to dive. Our dive skiff followed the submersible as it was being towed toward the dive site nearby, and as we rounded the tip of Isla Manuaelita, a small islet on the north side of Cocos Island, we could see that the current wasn’t nearly as bad as the previous day. (On that day, the towed submersible barely made any headway at all against the three-knot current.) So we decided to give it a try.

Shmulik Blum (left) pilots DeepSee as Dr. Michael Berms (right) looks on and I (center) cling to the outside on the way to the summit of “Mt. Everest”. Photo: Tricia Berms.

Our drop-point was a large and striking undersea pinnacle known as Mount Everest — the same site I had been to earlier on this trip inside Deep See. This time, instead of riding inside the sub, Howard and I would cling to the outside and ride it down to the very summit of the pinnacle at a depth of about 150 feet.

Although I had been in the water with submersibles before, this was the first time I used one as a taxi to take me straight to the dive site. It would have been nearly impossible for us to hit this spot without the sub. Although the current was not as strong as the previous day, it was still a solid 1.5 knots, which is enough to tear your mask off if you are sideways into it.

The summit of Mount Everest is tiny, so finding it after dropping down through a current like that would have been almost impossible. Deep See, however, has powerful thrusters, onboard sonar and an extremely talented pilot, Shmulik Blum, so within a couple of minutes after leaving the surface, the undersea mountain appeared out of the gloom in front of us.

Michael and Tricia Berms were inside the sub along with Shmulik, and along with Howard and me on either side of the acrylic sphere, Deep See carried a plastic basket containing a heavy anchor with several hundred feet of rope tied to its aft “deck” as cargo.

When we reached the summit, I transferred the anchor to the rock and sent the free end of the rope up to the surface so we could use it as a marker on future dives. Howard and I spent the rest of the short dive exploring the summit while Shmulik kept the sub nearby. Our main mission on that dive was to set the anchor and test the concept of riding the sub, so we stayed shallow and kept the bottom time short.

After that successful dive, we filled our rebreather cylinders with a special mixture containing 10 percent oxygen, 50 percent helium,and 40 percent nitrogen (a k a Trimix 10/50) in preparation for the deep dive. The team consisted of Howard, Shmulik and myself. Avi Klapfer piloted the sub, with Shaun MacGillivray, managing director of One World One Ocean and D.J. Roller of MacGillivray Freeman Films as passengers.

Once again, we rode the outside of the sub down to the summit of the pinnacle, and we were happy to see the anchor line still in place from the previous day. This time, I had my camera with me, so I immediately began filming the myriad fish surrounding us. Amid a forest of black-coral trees, I saw a glint of electric blue as a spectacular juvenile damselfish darted through the black coral branches. Close inspection revealed it to be a juvenile silverstripe chromis (Chromis alta), not previously recorded from Cocos Island.

For the next half hour, Howard, Shmulik and I swam around the western face of the undersea mountain, marveling at the almost incomprehensible abundance of fish species, while Avi kept DeepSee nearby. At one point, a giant school of amberjacks (Seriola rivoliana) enveloped me and I lost sight of my diving companions, the submersible, the pinnacle, and essentially everything else. It was magnificent.

Thousands of Pacific creolefish, paranthias colonus, fed on plankton far above us, near the summit. Dozens of other species — from tiny Cocos blue banded Gobies lythrypnus cobalus, flitting about the reef, to the massive yellowfin tuna, thunnus albacares, patrolling on the edges of visibility — played out their daily roles on the reef. But as amazing as the fish life was, the most thrilling aspect of the dive for me was how successful we turned out to be in combining rebreather diving with a submersible. I am now more confident than ever that this represents an extremely powerful combination of technologies for exploring the coral-reef twilight zone.

At a depth of 250 feet (76 meters) along the face of “Mt. Everest,” I use my video camera to document an unidentified damselfish among some black coral.  Photo: Howard Hall.