"Do you believe that Patrick McDermott is alive?" INSIDE EDITION asked private detective Philip Klein.
“Yes, I believe it,” he said.
Read: Ex-White House Chef Discovered Dead in New Mexico Mountains
It's a stunning claim about an enduring mystery - what happened to Patrick McDermott? He's the Hollywood cameraman and longtime boyfriend of beloved entertainer Olivia Newton-John, who disappeared 10 years ago this month.
McDermott went missing during an overnight fishing trip in the waters off Los Angeles in 2005.
A Coast Guard investigation determined McDermott had "most likely drowned.” But private detective Philip Klein, who's researched the case for a decade, said the Coast Guard is wrong.
“There was no way he could have fallen off. There was no way he could have jumped to his suicide. They would have known immediately,” he said.
INSIDE EDITION brings you images of the boat McDermott was on during his fateful trip. He even bought a meal during the last half hour of the cruise.
Some witnesses said they thought they saw McDermott walk off the boat, but they weren't sure. Investigators found his car parked at the marina. His keys, wallet and passport were still on the boat, raising speculation that he faked his own death.
Read: Theories Circulate Over Missing Malaysian Airplane
McDermott had recently declared "declared bankruptcy" and faced "back child support payments" to his ex-wife, CSI actress Yvette Nipar.
Right from the start, investigators wondered whether McDermott decided to walk away from his life and was actually alive and well.
Newton-John even spoke of that possibility a year after he went missing. "We'd be thrilled if it was true," she said.
Over the years, there have been several sightings of McDermott, including in Salulita, a small fishing village near Puerto Vallarta in Mexico.
Several people recognized McDermott when INSIDE EDITION showed them a photo. "I saw his face around town a few times. It's such a small town," said one person.
"He's been on this boat more than once I believe," said another.
Klein claims he nearly caught up to McDermott in Salulita. “We got within 48 hours of him,” he said.
Klein theorizes that if McDermott is alive, he may even be working for a criminal drug cartel. “I believe he's probably working for people in Mexico that probably don’t like publicity,” he said.
McDermott’s ex-wife believes he's dead and has called the detective "a serial liar (who)
is simply looking to be famous at the expense of an unfortunate tragedy in our lives."
Still, Klein is convinced that the man who once dated one of the most popular entertainers in the world will eventually be found.
“Somewhere, somebody will come up with those answers and we'll be there to get him,” he said.
Watch Below: Search Continues for Missing Amtrak Passengers After Derailment