“THINK before you jump.” That was the message from police divers and the Environment Agency who pulled four bikes, an axe, a laptop, and some scaffolding from the River Thames at Godstow Bridge in Oxford.

They organised the dredging session on Wednesday to warn river jumpers they could be seriously injured or die if they land on hidden objects lurking beneath the murky waters of the Thames.

Insp John Ramsbottom said his team of police divers recover all sorts of objects from the river every year, from bodies to shopping trolleys, firearms to broken glass.

He said: “River jumping is not a leisure activity, it’s very dangerous. I remember someone impaling themselves after jumping off Shillingford Bridge about five years ago.”

Other popular jumping spots include Donnington Bridge in Oxford, Shillingford, and Wallingford Bridge.

Dangers include the speed of the water flow, which can sweep even strong swimmers downstream, shallow waters, and boats, whose owners often find it hard to spot swimmers.

Russell Robson, principal recreation officer for the Environment Agency, said Godstow Bridge was a popular jumping spot, as it was near Wolvercote village and close to a pub.

He said the agency did not want to spoil anyone’s fun, but urged them to use the river safely and responsibly.

Mr Robson said: “It’s a popular bridge for people jumping off in the summer months.

“People are wanting to have a good time but they don’t really know the implications.

“We know it’s a thrill and it’s something that people have always done, but that thrill can end up in a nasty injury.

“Stuff that has been thrown in miles upstream can flow down and there are tree roots under the water.”

Matt Strange, the Environment Agency’s waterways technical officer in charge of patrolling and enforcement on the river, said he received about six calls a week during the summer from members of the public worried about bridge jumpers.

He said: “In my experience it’s primarily young teenagers but we do get some older people in their 20s and 30s.”