Kevin Decock is a man possessed. A man with a mission. Who won't give up until he finds the answers to a mystery that lies at the bottom of the sea.

His quest is rooted in the crash of a float plane along the British Columbia coast in the winter of 2005. The five men aboard -- the pilot and four loggers, two of them Decock's brothers -- died in the crash.

The search for the missing Beaver plane lasted only three days, called off after the body of passenger Dave Stevens washed up on the shore of Quadra Island, only a few minutes flying time from the Campbell River point of departure. According to police there is no hope of finding the others alive.

No other bodies are recovered. And the wreckage lies lost somewhere along the coast, probably at the bottom of the Georgia Strait.

Within weeks investigators from the federal Transportation Safety Board declared that the crash was caused by bad weather and possible pilot error -- a finding the families question. They band together with a vow that they'll get to the bottom of what caused the crash.

For Kevin Decock that vow has meant three years searching for answers. Three years searching the seabed for the missing plane and its passengers.

Working with volunteers from the community and a sonar expert he criss-crosses the Strait, a delicate grid looking for the tell-tale shape of a sunken float plane.

In July 2005 - success. The unmistakable shape of a float plane is spotted on the bottom. Cameras sent to the bottom confirm it is the plane. And then, on July 28, a recovery operation brings up the wreckage.

But it's bittersweet - no bodies are recovered. And the oil-spattered fuselage suggests the plane may been brought down by engine failure; perhaps a heroic landing in the choppy waters, only to sink with no rescue for those aboard.

The wreckage is examined, but despite all the efforts, the engine - a key component to determining what caused the crash -- has broken free and still lies deep beneath the waves.

Kevin Decock resumes his quest, once again trolling Georgia Strait in a borrowed boat, now searching for the 300 kilogram engine 230 meters underwater.

He spends months dragging the ocean floor with a fishing camera and a special hook on the end of a 350 metre cable.

"You've got to kinda picture in your mind that being eight hundred feet up is like being in an eighty story building and dropping a line off," explains Decock.

The kind of equipment he needs is not something you buy at the local hardware store, so Decock invents his own. He crafts a series of hooks, constantly modifying and redesigning them. Finally he comes up with model with a fin that sails straight through the water, while dragging the bottom - hopefully to catch, and eventually lift the engine.

He uses old weightlifting bars found at a scrap yard, bends them, cuts them to size and welds them together. Decock attaches a fishing camera connected to a small TV in the boat. With this, Kevin maps every square metre of ocean floor never doubting that eventually the engine would appear on his screen.

"Oh, you go bug-eyed. I mean you stare at it 10-14 hours a day sometimes but every second is crucial," says Kevin. "You don't want to take your eye off it for a second because a matter of being just a foot over and you could miss it," he continues.

For months upon months Kevin carries on like this, until September 2007, when miraculously - the engine appears across his screen and he watches the hook catch.

The engine of the plane is seen after being examined by the Transportation Safety Board.

"When the hook kind of just went right in and I let the current finish it, it just kind of sat there and then it pulled itself in. I let out a pretty good scream," recalls Decock.

Family members have been waiting for this moment for a long time, one more than any other - Sally Feast, sister of the pilot, Arnie Feast. She hopes the engine will show evidence of a mechanical fault, clearing her brother of any fault

"Kevin is the best fisherman on the west coast," Feast says of Decock. "He dragged the bottom and hooked a big one."

Sally Feast's brother was the pilot of
the float plane that crashed.

With the help of local loggers Decock hoists the engine to the surface. Then he loads it onto his pickup truck and takes it to the Transportation Safety Board offices in Vancouver.

While the families have long believed a mechanical failure must have brought the plane down, the T.S.B.'s investigation proves otherwise.

"We've concluded that the engine was intact and operating normally at the time of impact," says Bill Yearwood, Regional Aviation Manager for the T.S.B., who oversaw the engine investigation.

This is not the answer Feast or the families were hoping to get.

"It hurts because not for one second to I believe that just because they don't see it that it's not there," she says.

Still refusing to accept the official findings, family members now say they'll take the engine parts to their own experts. Despite the hundreds of thousands of dollars its costing the families to investigate the crash, they continue to soldier on.

And Kevin Decock has returned to the waters off Vancouver Island, his quest unfinished. He's again criss-crossing Georgia Strait -- now looking for the bodies of family members never recovered after the crash.