The first piece of one of the largest offshore wind farms in the UK was being sunk into the seabed off Great Yarmouth on Tuesday.
The bases of the turbines are being sunk into the seabed
For the last few days construction staff for developer Powergen have been preparing to start work on the 30 turbine wind farm at Scroby Sands.
They had hoped to begin on Monday, but had to carry out further safety checks.
On Tuesday they were sinking the first of the turbine bases for the £78m wind farm using a giant hammer.
There are 30 bases in all, each measuring 40 metres across and 50 metres in length, and weighing 200 tonnes.
It will take between one and three hours to sink each base into the seabed.
The wind farm was approved by the government in April 2002 to provide power for 50,000 homes.
It is part of the government's plan to triple the amount of energy generated from renewable sources by 2010.
Project manager Andy Hilton said the building work had been delayed because of safety concerns and because the tide had not been right for the vessel to be used in the construction of the wind farm to set sail.
He said: "We managed to get to get the vessel out on Saturday but some modifications that were done offshore when we put the pile in place didn't seem to be working.
"So from a technical point-of-view and a safety point-of-view, we decided to abandon the operation."
There are also plans to build wind farms in the Wash, off the coast of Cromer, and in the Thames Estuary.