A “marked increased” in visitors to the deep gorge at Finnich Glen has led to a “significant rise” in emergency call outs, a spokesman from Lomond Mountain Rescue Team (MRT) said.
The rise follows the appearance of stunning natural feature near Killearn in film and television, as well as print and online media, he added.
The gorge, said to have been a meeting place for druids, featured in season one of Outlander as well as Roman-era film The Eagle.
Recently, it was filmed for BBC Scotland’s The Social when wildlife presenter Andrew O’Donnell floated through the water on an inflatable kayak wearing a red loincloth to mimic Mowgli from The Jungle Book.
A spokesman for Lomond MRT said: “During recent weeks Lomond MRT has seen a significant rise in call outs to the stunning natural feature of Finnich Glen and the Devil’s Pulpit.
“The marked increase in visitor numbers has followed the gorge featuring in several recent appearances on film and television, in print and online.
“A visit to the Glen can be a memorable experience but we would like to bring to the publics attention several safety concerns and potential hazards.”
The spokesman said that visitors wanting to travel the full end of the gorge, which drops nearly 70ft into the river, required skills in swimming in canyoning.
“There are very few points where it is safe, or indeed possible, to climb out,” he added.
“Despite it officially being the summer, the water is cool and its level rapidly rises after heavy rain.
“Consequently hypothermia is a real concern if you are not suitably clothed.”
No mobile phone reception exists in the depths of Finnich Glen.
It is understood that Lomond MRT has attended four emergency call outs to Finnich Glen since May, with the last rescue taking place two weeks ago.
“Each has involved quickly extracting cold, wet and trapped visitors by raising them vertically up the mossy, wet walls by rope,” the spokesman said.
The Devil’s Pulpit starred in Outlander when Dougal MacKenzie used the “truth-inducing waters” to make sure he trusted lead character Claire Randall.
The warning also comes after an influx of visitors was reported at Clava Cairns, the Bronze Age burial and ritual site near Inverness, which is said to have partly inspired time travelling fantasy Outlander.
Reports of people climbing on the stones to carry out seances have been made, with claims of vandalism and graffiti.