Swimmers in West Yorkshire have taken a dip in a reservoir to protest about being banned.
British Waterways has put up a "no swimming" sign at Sparth Reservoir in Marsden, Huddersfield, claiming it is a replacement for previous signs which had gone missing.
It claims it would be "reckless" to allow swimming at the site.
But swimmers said they have used the reservoir for decades and it is possible to enjoy the sport safely.
They believe the reservoir has been used for recreational swimming since the 1940s and possibly earlier.
In the future they hope signs could be changed to allow them to swim at their own risk.
Leisa Grey, from Marsden, has been swimming at the site for about seven years.
She said: "I cant believe they've done that after all these years. To have no community consultation on it, I was really angry about it."
British Waterways said bylaws prohibit swimming at the site even if signs are not present.
David Baldacchino, from British Waterways, said: "We don't manage our waterways as swimming pools. This is a 200-year-old industrial site with structures buried in the water and currents that could suck you into a valve.
"I think anyone swimming there and ignoring these issues, or worse, encouraging their children, is being pretty reckless."
Referring to calls to allow people to swim at their own risk, he said "People can't always know all of the risks."
British Waterways said in "exceptional circumstances" bylaws could be used to prosecute swimmers.