Ill-equipped pleasure boaters have been warned after lifeboat crews were scrambled to rescue three men in a wooden boat who only had mobile phones.
While most of the North East basked in sunshine on Monday, thick fog hugged inshore waters off Teesside.
The conditions caught out an open wooden boat with three men on board from Hartlepool.
They were eventually found by chance after a three-hour search operation, involving five rescue vessels.
The Royal National Lifeboat Institution (RNLI) said the search was hampered by the crew's reliance on a mobile phone rather than a radio.
RNLI spokesman Dave Cammish, who is based at Redcar lifeboat station, said the boat was left stranded without radio, power or navigational aids.
They wore only shorts and t-shirts and carried no life jackets.
Mr Cammish said: "We really were looking for needle in a haystack.
"We didn't get very much assistance from the vessel in that they had next to no equipment that would assist us in any way.
"It was only by chance that the boat drifted past a navigation buoy, which enabled us to get to it quicker."
Mr Cammish said the boat could have been struck by larger commercial vessels which use the area as an entry to Teesport and Hartlepool.
He said the wooden boat could have "finished up as matchwood".
He added: "This underlines the dangers of this increasing trend towards taking a mobile phone to sea instead of a proper radio.
"Mobile phones are not meant to be used for communication at sea and anyone who relies on them is really taking their lives in their hands."