Two teenagers who went camping during Storm Francis got stuck when they were surrounded by a "raging torrent of water", rescuers said.
The pair walked out to an island on the River Dart, in Devon, but were surrounded by rising water overnight.
They were spotted on the "very remote" islet by two "highly proficient kayakers" who raised the alarm.
Incident commander Matt Johnson said the young men were "extremely grateful" to be rescued.
'Stuck for days'
Mr Johnson, of Devon & Somerset Fire & Rescue Service, said it had "poured down" throughout Monday night after the pair had set up camp.
"There was a raging torrent on both sides and they had no phone signal, they were very worried and very scared," he said.
He said the river is known to rise "very rapidly", and "the concern was it would either rise over the island or they would be stuck there for days".
About 30 people were involved in the operation to save the young men on Tuesday.
They were brought to safety in a small boat, tethered in three directions, which rescuers towed towards land.
Mr Johnson said it was a reminder for people not to do "what they want to do regardless of weather conditions and warnings".