A young navy sailor was dramatically plucked to safety by a police officer after falling overboard in freezing conditions.
The 19-year-old able seaman fell from HMS Diamond into Portsmouth Harbour while on duty in the early hours of Monday.
The water was so cold, the freezing sailor was unable to move as a Ministry of Defence police launch crew fought to rescue him in sub-zero temperatures.
Fearing that the man was going to freeze to death, one police officer bravely removed his life jacket and dived into the sea to rescue the sailor, who was then taken ashore to a waiting ambulance.
He is now recovering in Queen Alexandra Hospital in Cosham.
The drama unfolded shortly after 2.30am on Monday when the sailor, who has not been named, fell between the quayside and the stern of HMS Diamond - the navy's newest Type 45 warship, which is alongside in Portsmouth.
Navy colleagues called for help and threw the sailor a line to cling on to as he bobbed in the water, which was just 5C.
A police launch boat arrived five minutes later and cut its engines to move in close to the stranded sailor.
Inspector Andy Acock, commander of the MoD police marine unit, said: 'He had no strength and hypothermia was not far off.
'We lowered the platform to get him on the boat but he was unable to assist himself at all.
'We gave him a rope to pull himself in but it wasn't happening.'
With the sailor struggling in the water, one officer, who has not been named, decided to dive in and get him on to the boat.
A police colleague said: 'It was freezing cold. It was touch and go whether he'd survive before we got him out of the water. He wouldn't have survived if he'd been in the water much longer.
'An officer took off his life jacket to free up his arms and jumped in to save him. It was an extremely brave move and it's saved this man's life.'
Insp Acock said: 'I've got nothing but praise for that officer. To dive in the water, especially at this time of year, is commendable and has saved this man's life.
'But it's part of the job and I'd like to think all my officers would have done the same had they been in that situation.'
The sailor collapsed when he got aboard the police vessel, Insp Acock said.
'From our initial assessments there were no physical injuries - just shock and the onset of hypothermia,' he added.
The navy said it was 'too early' to say whether an investigation will be launched to determine how the incident happened.