Mount Clemens — It was a date made for summer: a leisurely cruise, dinner on shore, and back on a tranquil lake.

Then, he went overboard, with the boat still running, into Lake St. Clair, leaving her behind.

She frantically called 911, unsure if he was alive, where she was and how to stop the cruiser. Did he fall in? Jump? It's unclear, and police are as perplexed as anyone, even after safely retrieving him.

"We're extremely surprised to have found him alive," said Sgt. Patrick Maceroni, spokesman for the Macomb County Sheriff Marine Division.

The Macomb County Sheriff's Marine Division and Dive Team arrived at 8:10 p.m. Monday, where they found the woman, who has not been identified by police, about 2½ miles from the Clinton River in Harrison Township.

Hours later, the man would find police, a feat they would later say was unusual.

The woman told deputies the 43-year-old man from St. Clair Shores invited her out on a 40-foot boat for drinks and she agreed. They spent most of the day on the lake and stopped at a restaurant. After their meal, she asked the man, who was not identified, to take her back to shore.

That's when the date went adrift.

"She believed the male became upset because he then left the captain's seat while the boat was moving and jumped into the lake," the Macomb Sheriff's Office said in a news release.

More: Divers search for man who jumped from boat into Lake St. Clair

The woman, whom police haven't identified other than saying she was also 43 years old, called the authorities and said she was unable to stop the craft and was unfamiliar with Lake St. Clair.

After deputies located the boat, they jumped aboard and stopped it, eventually ferrying her and the boat to shore.

The Marine Division's Dive Team started a search for the man. Hours later, a man approached a deputy in a powerboat at 1 a.m. Tuesday. It had been a four-hour search in 72.5-degree water temperatures, according to weather service data.

"The male on board told them he was the man they were looking for," police said.

He told authorities he fell overboard miles from the county boathouse, where the marine division is housed, and swam to Strawberry Island. Unable to locate anyone on the island, he "commandeered a boat" and drove to the marine division boats on the lake, deputies said.

Macomb County Sheriff Sgt. Renee Yax said it was a case of he said-she said.

"She said he jumped, he said he fell; we don't have a belief either or," she said.

Despite the woman's claim that they were drinking during the day on the boat, Yax said the man was not intoxicated when they found him.

"He went overboard and swam to an island, where he found a power boat," she said. "He didn't steal it, he only took it for his own rescue."

The errant boater was taken to shore and examined by emergency medical personnel. Officials took the man to a hospital to be evaluated.

Deputies said they completed their investigation into the incident and are not seeking criminal charges.

Maceroni said it's unusual to have a successful outcome.

"Depending on where he went in, it's a decent swim to Strawberry Island," he said. "It's still pretty cold, so you can't be in there for hours because you risk hypothermia.

"Nine times out of 10 it ends in a death," he said.

Detroit News Staff Writer Payne Lubbers contributed to this report.