A lifeboat crew was called to a report of a capsized boat off Hartlepool on Saturday.
Hartlepool RNLI sent its inshore lifeboat to the Longscar buoy, off Hartlepool, at 1.55pm.
They discovered what was believed to be part of the actual Longscar East cardinal buoy, which had been damaged during the recent stormy weather.
The inshore lifeboat was stood down and returned to the Ferry Road lifeboat station at 2.07pm, before being made ready for service by 2.20pm.
Hartlepool lifeboat operations manager Chris Hornsey praised the volunteer crew for their quick actions.
He said: “Despite freezing cold temperatures and challenging sea conditions, the inshore lifeboat crew were quick to respond and along with our local Coastguard colleagues quickly brought the incident to a close.”