Equipped with powerful magnets, history enthusiasts and environmentalists scour France’s rivers, pulling out bits of scrap metal, bikes, scooters and the odd kitchen appliance.
Sometimes, too, they fish other more unexpected objects out of the water, such as unexploded munitions.
Magnet fishing has fast become a popular pastime, according to public safety officials, but French authorities have clamped down over fears that historical battle sites could still harbour active weapons.
As in other countries, participants in France tie a super magnet to a rope and drop it into waterways, partly for treasure hunting, partly for environmental reasons.
On the banks of the Oise river, in a town about 75 kilometres north of Paris, Owen Gressier, 20, and his three fellow magnet fishermen cast their neodymium magnets.
After several attempts at their spot near a bridge in La Croix-Saint-Ouen, they latch onto something.
It takes a few minutes to haul out the item with the help of a grappling hook.
A rusty, cast-iron pipe emerges: ‘Nice catch,’ they say. It’s the best find that afternoon.
‘We’ve been fishing here for a number of years, the bottom is pretty clean,’ Gressier, a forklift truck operator, says.
Driven by what he calls his passion for World War II and a quest to find medals, military gear and other historical objects, Gressier says that he also ‘quickly realised that it was possible to clean up the waterways’.
In 2017, he set up a Facebook page, which now has more than 500 subscribers, where members share photos, advice and organise outings.
In the neighbouring Somme department, site of one of the largest battles of World War I, Christophe Devarenne started magnet fishing three months ago.
He says the thrill comes from ‘not knowing what will be at the end of the magnet’.
In other French regions too, where bloody battles were fought during both world wars, magnet fishing enthusiasts have discovered shells, ammunition and grenades.
And they can still be active, warns the national public safety authority.
Gressier said that his group had hauled out one active shell and hundreds of rusty weapons but knows what to do in that case.
‘We establish a security perimeter and we warn the disposal experts,’ he adds.
Despite the warnings, his group says it won’t stop the activity that has got them hooked.
‘Nobody is really afraid, because the police have better things to do than chase after magnets,’ he adds.
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