If you think searching for a needle in a haystack sounds difficult, try looking for a priceless ring on the bottom of Sydney Harbour.
That's the kind of task relished by a rare breed of "beachcombers".
Beachgoers often leave the surf or sand feeling refreshed but missing a piece of jewellery or a set of keys.
For beachcombers like Sydneysider Michael Oliver, a subsequent desperate phone call is when the treasure hunt begins.
Oliver, 33, first used a metal detector when he was 10 years old. Since then he's scoured beaches, lakes and rivers to help retrieve lost treasures.
Two years ago he turned his hobby into a part-time business and now he finds objects for a fee.
Rings, watches and coins are the main items he recovers. He's located an 18-carat gold ring and a gold-plated pocket watch from the 1920s but also stumbled across bullet shells and old cast iron toys.
"Every time I go out, I find something, especially when I go scuba diving," Oliver told AAP.
"When you start finding that stuff, you just have to keep working the area, you call that a honey hole."
Oliver combs beaches across Sydney and has gone as far north as ther Central Coast to help a beachgoer find a lost item.
Sydney's iconic Bondi Beach is the biggest treasure trove, followed by Shark Beach on the harbour.
"For me, it's a hunt, I love the hunt," he says.
"If you tell me you've lost a ring and given me an approximate location, I basically don't give up until I get frostbite."
The 33-year-old recently found someone's $50,000 engagement ring.
As well as rediscovering treasures he also comes across a lot of trash.
At Little Bay in Sydney's eastern suburbs, he estimates he's picked up at least 50 kilograms of waste.
Nick Richards scours beaches in northern NSW and helps people who've found him via theringfinders.com.
He too says beaches end up a lot cleaner after he's scoured them.
"Treasures go in my left pocket and trash in my right - my right pocket always ends up fuller than my left," he told AAP.
Richards has been beachcombing for 20 years and says it's an amazing feeling to find something someone thought was lost.
He doesn't charge but instead asks people to donate to a charity.
He's been asked to find boat propellers and even boats themselves.
"It's mainly jewellery but I've also found sets of teeth, pre-decimal coins and toys," he says.
Richards claims he won't stop searching for something until it's found - which has seen him scuba dive 30 metres down in Sydney Harbour to successfully retrieve a platinum wedding ring.
If Richards and Oliver aren't called to retrieve lost belongings on NSW beaches then it's likely local councils are.
Northern Beaches Council workers have come across everything from a barnacle-covered turtle and green algae balls to coconuts and pumice stones from an underwater volcanic eruption.
South of Sydney, Wollongong City Council lifeguards have discovered life-jackets, an esky containing beer and a shipping container.
Twenty years ago, a VW Kombi van that had been swept into a creek ended up on North Wollongong beach a few days after huge floods destroyed the region, a council spokeswoman told AAP.
Dead animals have also been found on beaches over the years including two whales, dolphins, sharks, seals, dogs, cats, a deer and a cow.
But, sadly, spokeswomen for both councils concede the most common item retrieved by lifeguards is rubbish.