A man tried to swim for it after a police chase around the edge of Brighton ended in an eight-car crash.
He was arrested as he emerged from the freezing water and taken to the Royal Sussex County Hospital in Brighton.
The eastbound side of the A27 was closed for more than six hours after the pile up, causing rush-hour jams, with a long tailback and a slow queue crawling through Lewes.
The police chase started on the A23 as a stolen Mercedes was spotted speeding south towards Brighton.
The driver rammed a police car at Patcham and sped off towards Lewes where the chase ended in a crash.
Sussex Police said: “A man was arrested after swimming across the River Ouse in Lewes following an eight-vehicle collision on the A27 on Wednesday afternoon (7 February).
“Three men ran from the Mercedes, which had been reported stolen from south west London, after it crashed near the Southerham roundabout at 4.12pm while being pursued by police after being spotted travelling at speed on the A23 a little earlier.
“One managed to swim across the river in attempt to evade capture but was picked up by police as he emerged on the opposite bank.
“He was taken to hospital under arrest, along with another of the car’s occupants who suffered an arm injury in the collision.
“The driver of another vehicle involved in the collision sustained a suspected broken collarbone and was also taken to the Royal Sussex County Hospital in Brighton.
“The pursuit had commenced on the A23 just north of Pyecombe, before the car turned on to the A27.
“It rammed a police car at the A23/A27 interchange before continuing on towards the eastern end of Lewes bypass where it crashed, damaging a number of other vehicles.”
Sergeant Stacey Ellott, from the Surrey and Sussex Roads Policing Unit, said: “We are aware that this caused considerable disruption and we worked as swiftly as possible to reopen the road but this did take some time and we thank people for their patience.”
The eastbound stretch of the A27 was reopened at about 10.30pm.
Sussex Police added: “Anyone who witnessed the collision or any of the incidents leading up to it is asked to report online or call 101 quoting Operation Raydon.”
