Posted Wednesday, July 14, 2010 -- 10:00 p.m.
By NBC15's Dana Brueck

This is a closer look at a Rock County mystery: the mystery of what happened to a Janesville doctor missing for almost eight years.

People who knew Dr. Michael Black say this is perhaps where he felt most at peace -- somewhere deep below the water's surface.

"Diving was something he really enjoyed," Rob Stroud says, "If he was stressed or depressed, that would've been a natural outlet for him."

"We were both into diving any time any conditions," Stroud says.

Rob Stroud met Black through the Madison-area's Four Lakes Scuba Club.

"He was one of the few members of the club that liked to dive locally," he says of Black.

No matter the season, Stroud and Black also shared a passion for wreck diving.

"He was someone you could safely dive with because was very careful."

The month before the Janesville ophthalmologist disappeared, he, Stroud and another diver organized one of their many trips.

"October of 2002, we planned to go over to Lake Michigan... and do three different wrecks near Milwaukee."

But rough water forced the group to scrap its plans. The men decided to leave Lake Michigan for Lake Geneva.

"... and... dove on a wreck there... three of us went to a restaurant and we were talking about well, it's the end of the season for the Great Lakes."

"I expected the next time we'd go diving would be in the Spring."

But there wouldn't be a next time. Michael Black was reported missing November 20th of 2002.

Janesville Police Detective Erik Goth says Black's truck and empty boat trailer turned up at a Milwaukee marina.

"And in December, his scuba gear and oxygen tank with his name on it turned up in Michigan on the shore of Ottawa County."

But Black's boat has never surfaced anywhere.

"Where it is would give us some information as to his whereabouts possibly."

"But with the amount of articles and bodies, and body parts, that do show up, I did expect we'd have something," Goth says.

"It would be nice if we could put some closure on it, you know."

Shortly after his disappearance, a memorial service was held at Kiwanis Pond, where Black was a regular diver. His dive pals have their ideas about his final resting place.

"It wouldn't surprise me if his body was found near a wreck... that's where he would've gone if he was in Lake Michigan. He would've been on a wreck and he knew where they all were," Stroud says.

But Black has never been found, leaving Det. Goth with a case he cannot close.

Was it a case of suicide? "It's not that he wouldn't dive alone, but he didn't take unnecessary risks," Stroud says.

Black had lost his job at a Janesville clinic before he vanished.

But his brother says Michael planned to play tennis two days later and planned to attend Thanksgiving dinner.

Or, was it an accident?

"He never went diving without checking his equipment first," Stroud says.

Or a case of a new identity?

"There is that possibility that was all a setup or staged.. .and he may be living his life somewhere else," Goth says.

Michael Black's brother says a judge ruled the death accidental, for insurance purposes.

But the case remains open, with Janesville Police seeking any information.