Police in Preston traced a Range Rover reported as stolen to a spot close to a derelict pub - but the suspect threw the keys in the River Ribble.
It led to underwater search officers having to sift through the river, close to the old Shawes Arms pub on London Road, to try and find the keys.
They eventually reclaimed them after a lengthy search, having arrived at the scene at noon today.
The driver, a 20 year old from Preston, was arrested on suspicion of theft of a motor vehicle and burglary.
He is still in police custody.
Anyone with information can call the police on 101 quoting incident reference 513 of January 11th.