You often see them beeping along the beaches: mainly men, and the odd woman, with metal detectors.
But if you think they do it for the money, think again - a lot of them do it for love.
When Mava Enoka went to her local beach for a swim, she wasn't expecting it to restore her faith in human nature.
"We decided to have a lovely family day at the beach and jumped in the water," she told Seven Sharp.
"I thought it would be a great idea to look for some pipis… and was putting my hand into the sand, and at one point I pulled it out and said, 'Oh, my ring's gone.'
"Panic was the first emotion - I had no idea where I had lost it."
Ms Enoka had lost her engagement ring in the waves and she had completely given up hope of finding it, when a complete stranger came to her aid.
Seven Sharp was about to reunite her with that stranger yesterday morning when a funny thing happened: the ring went missing again.
Instead of a lovely reunion, Ian Scott was back to lend a hand.
He's a detectorist and a member of NZ Ring Finders.
Ms Enoka's husband Jason was the one to track him down the first time.
He was devastated when the ring went missing, having chosen and bought the ring for his partner.
His online search led him to NZ Ring Finders and Mr Scott.
"It's just a group of people, a list of people who are prepared to go in their own time as volunteers to find people's lost stuff," Mr Scott says.
Mr Scott, a quiet, humble, man who by day works in healthcare, coordinates the team.
"We've got 60 [people] around the country. They've got different skill levels. Some people can metal detect in a park, other people can wade up to their waist, other people can scuba dive up to three metres, even deeper."
Ms Enoka's ring was found after two weeks. Four people attempted to find it before Mr Scott came up trumps.
Mr Scott says he does it for the thrill of the hunt.
"Not knowing if I'll find it, and having somebody that's absolutely happy and excited when you've found it because they believed it was lost forever."
Ms Enoka says she was stunned speechless when Mr Scott got in touch.
"When we got a message - and the message was just a photo... we were just speechless for about 30 seconds. We couldn't believe that someone had found it."
And ever helpful, Mr Scott was able to track down the ring again with his trusty metal detector yesterday.