Adventure-seeking teens are risking their lives by swimming in reservoirs brimming with hidden dangers, a farmer has warned.

Great Yarmouth Mercury: A fence put up around a reservoir in Caister has not deterred teenagers looking for adventure Picture: Liz CoatesA fence put up around a reservoir in Caister has not deterred teenagers looking for adventure Picture: Liz Coates (Image: Archant)

Tony Oakley says he has seen a spike on the number of mainly boys wrecking his crops by dragging bikes across fields to access open water at Caister.

Cold-water shock, weeds, and steep, slippery sides make for a dangerous day out, the 51-year-old said, some of the lads even taking inflatable boats and dinghies to the remote site.

Underwater pipes added to the drowning risk at an isolated spot emergency services would struggle to access, he added.

Mr Oakley said he had intercepted and confronted at least six different groups in the last three months, all boys on bikes.

Great Yarmouth Mercury: The irrigation reservoir at Caister is a water source for potato crops and a haven for wildlife, but not a playground for teenagers in the summer, a farmer has warned Picture: Liz CoatesThe irrigation reservoir at Caister is a water source for potato crops and a haven for wildlife, but not a playground for teenagers in the summer, a farmer has warned Picture: Liz Coates (Image: Archant)

"I just could not get through to them how dangerous it was," he said.

"In some places it is 5m deep. It is slippery and cold and there are underwater suction pipes to irrigate the crops.

"The thing is they do not understand what is underneath the surface.

"There are weeds growing and we have put fences up for their protection and to highlight the fact that there's a danger. The location is an issue too if the emergency services ever had to come.

"We have had six groups in three months and it is never the same boys.

"I think word goes about and the ones I have already told off do not come back but the ones that think they will chance there arm still have a go.

"I tell them it is private property and that they do not realise the dangers involved.

"There have been a couple of groups that have been a bit mouthy but the rest have been sheepish and apologised.

"I do not want to have to be the person that breaks any news to a parent."

As well as the risk to life there were financial considerations too.

To access the site near Caister Castle the teens had made a hole in a hedge and damaged crops, as well as the fence.

Any damage to the reservoir lining could run into thousands of pounds.

The stretch of open water is a hub for wildlife and at a scenic spot which looks tempting on hot days.

But ultimately it was a working farm on private property that was an industrial not leisure area.

"I'd never stop anyone having fun because there is not enough of it nowadays but this is dangerous fun.

"There are swimming pools and the sea to mess about in," Mr Oakley said.