Two teenagers were rescued by lifeboats after their dinghy drifted out to sea.
A 13-year-old boy and girl made the 999 call when they realised they could not make their way back to the Hove shore in the dark.
An inshore lifeboat was launched and coastguard officers used tri-angulation devices to track the location of the mobile phone signal.
The youngsters, who were only dressed in shorts and t-shirts, were suffering from the effects of the cold and shock when they were found south of the Babylon Lounge, Kingsway, Hove.
David Cassan of Shoreham RNLI Lifeboat, who was part of the rescue operation on Monday night, said: “The two wet, confused and very cold teenagers were aboard within just nine minutes of the launch.”
The pair were taken to Worthing Hospital for treatmentr after they deteriorated on board.
Helmsman Adam Cairns said: “As soon as the two casualties were taken on board the lifeboat their condition suddenly, and rapidly deteriorated.
“It's very common that when people need to be rescued the adrenaline is pumping round their body, but as soon as they see a lifeboat all the drops away and the actual conditions they've been fighting to survive catch up with them.
“There are cases where people have been in the water, seen the lifeboat, and we've actually lost them because all their will to fight drains away.
“Fortunately that didn't happen in this case but they were in an extreme state of shock.”
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