Sunshine revellers have been warned not to jump into the sea for a cool off - after a pier prank led to a rescue operation costing thousands of pounds.

A youngster who apparently flipped from the railings of Cromer Pier just after 9pm on Thursday night was rescued by the resort's inshore lifeboat.

Police, coastguard and ambulance were also involved. The young man did not need to be taken to hospital but was given 'advice' at the scene about his behaviour.

Today coastguards and lifeboat officials warned of the dangers of diving from structures into the sea or river.

Cromer lifeboat operations manager Richard Leeds said the rescued casualty was very lucky to escape serious injury.

'Jumping into 4ft of water at low tide from a height of 30ft can lead to back or neck injures - and you don't know what is under the water,' he said.

This year there had not been many incidents, due to the poor weather, but last year there was a flurry of 'tombstoning' incidents.

In the summer of 2008 a 33-year-old man drowned after jumping from the pier.

Mr Leeds said the latest rescue would have cost thousands of pounds, and potentially took emergency services away from more needy casualties.

North Norfolk coastguard sector manager Tony Garbutt added: 'These sort of incidents are often people being encouraged by others - and they don't realise the consequence so their foolish act until it's too late.

'You never know what is under the water.'

Coastguards have put up warning signs at tombstoning 'hotspots' such as piers, breakwaters and harbour walls.