SYDNEY (AP) - The shifts on board the ship are punishing: 12 hours on, 12 hours off, seven days a week, for a month straight - though pingpong and poker during the downtime help break up the monotony.
But for the American man who designed a sonar device being used in the hunt for Malaysia Airlines Flight 370, spending nearly six months at sea searching for the plane was something of an honor.
With that honor has come the weight of responsibility - for the families of the 239 people on board the vanished plane still desperate for answers. Now, with the search of a remote patch of ocean off Australia's west coast drawing to a close and the plane's wreckage proving stubbornly elusive, Jay Larsen is among those feeling the pressure.

"I think there is some tension building as the end of the job comes nearer," says Larsen, whose Whitefish, Montana-based company built one of the devices scanning a mountainous stretch of seabed where the plane is believed to have crashed nearly two years ago. "Everybody wants to find this thing, including us."
In this March 4, 2016 photo, Jay Larsen, who designed a sonar device being used in the hunt for Malaysia Airlines Flight 370, poses for a photo with a long range acoustic locating beacon, used to track the sonar device in Seattle. Larsen considers the nearly six months at sea searching for the plane something of an honor.

With that honor has come the weight of responsibility for the families of the 239 people on board the vanished plane still desperate for answers. (AP Photo/Elaine Thompson)
Larsen has been involved with the hunt from the beginning, when marine services contractor Phoenix International Holdings hired his deep-water search and survey company, Hydrospheric Solutions, to provide the sonar equipment used on board the search vessel GO Phoenix.
The Malaysian-contracted vessel participated in eight months of the hunt until June last year.

Most recently, Larsen and his team flew to Singapore to load their sonar device onto a Chinese ship, the Dong Hai Jiu 101, which has just joined three other vessels scouring the southern Indian Ocean for the plane. He then traveled on board the Dong Hai to the west Australian city of Fremantle, and, after ensuring the sonar and his team were ready to go, bid them adieu last month as they set out for the search zone 1,800 kilometers (1,100 miles) to the southwest.

Larsen's company has a crew of eight people on the Chinese ship who are tasked with running the sonar system - or "flying the fish," as he puts it. That "fish" is actually a 20-foot (6-meter) long, 5-foot (1.5-meter) wide, 3.5-ton bright yellow behemoth called the SLH ProSAS-60, which is dragged slowly behind the ship by a cable.

The device hovers just above the seabed as it scans a patch of ocean floor 2 kilometers (1.2 miles) wide, sending data to computers on board that process the information into images.

The black-and-white, near-photo-quality pictures that pop up on the screen resemble the surface of the moon. The imagery, produced by synthetic aperture sonar, is higher quality than conventional sonar, Larsen says, giving him confidence that his team won't miss the debris field if they drift over it.

The job can be grueling. Larsen was on board the GO Phoenix at the start of the underwater search - from September 2014 to February 2015 - breaking only to return to shore once a month for fresh supplies, and flying home once to the U.S. for the holidays.

"It almost ruined my head, my brain, my heart, my marriage, but we got it going," he says.
On board, two teams of three people work alternating 12-hour shifts every day, a job that requires close attention and coordination. One of Larsen's employees sits at the controls flying the sonar, while a navigator sits beside him looking at upcoming terrain to warn him of obstacles.
A third staffer sits in a nearby seat providing a backup set of eyes. Another team member pops in occasionally in case anyone needs a break.

The work is both monotonous and intense; there are long stretches where nothing happens, until bam - a massive mountain in the seabed suddenly appears in front of them. The sonar could be destroyed if it hits a rock wall, or it could get hopelessly stuck on something and languish forever on the ocean floor, which reaches depths of 6.5 kilometers (4 miles).

"It's that whole cliche of hours of boredom interspersed with moments of terror," Larsen says. "Some of the terrain out there is just incredible, these mountains and trenches and stuff that we're trying to get every last look into to make sure we don't miss anything. So the more daring we are, the better in terms of the imagery - but the consequences are real. ... It's a couple-million-dollar piece of equipment and we don't want to lose it."

Larsen's team must work closely with the crew to ensure the vessel is maintaining the right speed so the sonar doesn't sink to the bottom.
Those on board also must grapple with the region's notoriously brutal weather. The team can operate the sonar in up to 4-meter (13-foot) swells, but anything bigger forces them to pull up the gear so it isn't damaged. Maneuvering the massive device out of the water when the waves are big is tricky, as it can swing violently from the crane as the ship rocks.

Well-planned choreography by more than a dozen people is required to prevent anyone from getting hurt.
The first month Larsen's team was on the hunt, they were in a constant state of alert, expecting the plane would quickly be found. As time passed, some of that anxiousness waned and the job became more routine. But they've never given up hope that the aircraft will be spotted, even though there's just 30 percent of the 120,000 square kilometer (46,000-square-mile) search zone left to check.

"It literally could be any minute, we could look up and see debris on that screen," he says.
When Larsen's team isn't on duty, they burn off energy at the ship's gym, watch movies, read and play poker, pingpong and somewhat contentious rounds of Monopoly. But often, they prefer to retire to their rooms for much-needed solitude. Most people share a room with one other person, but work opposing shifts so they get the space to themselves.

The Dong Hai crew is planning to stay in the search zone for 38 to 42 days at a stretch before returning to port for supplies. It's a tough assignment, but Larsen didn't have any trouble wrangling volunteers.

"Everybody wants to be on the MH370 search," he says.
The job comes with some perks, such as the novelty of being the first humans to lay eyes on much of the underwater terrain. The seabed in the search zone is so remote that it had never even been mapped before the hunt for Flight 370 began. In that sense, the search has proven thrilling, though Larsen is conscious of the larger goal.

"There are 239 families out there, so it's hard to be like, 'We're excited! This is awesome!'" he says. "But at the same time, we're really proud right now to be a part of the search because it's a huge effort and I hope to bring resolution to those families. And that's really the thing that drives us all is, 'Put a lid on this thing. Let's get this done.'"

In this Feb. 10 2015 photo released by Hydrospheric Solutions, members of the Hydrospheric Solutions and Phoenix International Holdings search team launch the SLH ProSAS-60 sonar device from the GO Phoenix, a vessel that spent months searching for missing Malaysia Airlines Flight 370 in remote waters off Australia