If one man's trash is another man's treasure, then scuba diver Michael Pelley is a rich man.

He explores the bottoms of rivers and lakes, sifting through trash to find valuables people have left behind.

"I tell people that I'm a diver first and a treasure hunter," Pelley said. "It started out with me just going out there and looking for anything and everything."

His curiosity has morphed into a greater purpose: helping others recover objects that have sunk far below the water's surface.

"I also wanted to be able to return something if I did find it, and I could return it," he said. 

Pelley realized he was going to have to get his name out there, so he came up with Merman Mike. Pelley now takes thousands of YouTube viewers along with him on his dive missions.

Recently, he was asked to search for a woman's wedding ring that had slipped off her finger while she was at Bass Lake near Yosemite National Park. It was his deepest dive yet.

"I found cans, I found bottle tops and I found pull tabs. I found almost any and everything besides the ring," Pelley said.

It took nearly three hours of digging before he finally found the sunken treasure.

"You could see me looking at it for a second before I realized what it was, and then I just absolutely blew up with the excitement," Pelley said. "It's always the moment I'm looking for the most, especially if there are doubts."

Merman Mike says he doesn't charge to find items because moments like those are priceless.

"I tell everybody that I'm just happy to help anytime," he said. "My head goes underwater and I'm a happy camper."

Merman Mike also helps to clean the lakes and rivers he searches. He says you can't just go diving for the treasure — you have to also pick up the trash.