Lessons should be learned after a maintenance worker drowned at a Flintshire power station, the Health and Safety Executive (HSE) says.
Michael Benn, 37, from Fife, Scotland died after falling into a cooling tower at Connah's Quay power station in 2007.
His employer, Epsco Ltd, of Perth, Scotland, pleaded guilty to health and safety offences at Mold Crown Court and was ordered to pay a total of £155,000.
HSE, which prosecuted the firm, said the death "was entirely foreseeable".
Mr Benn, a contractor from Glenrothes, was one of a team of three working to remove sludge and debris from part of the cooling tower on 27 August, 2007.
A HSE investigation found he was working in poorly lit conditions inside the tower, and had gone into an enclosed culvert to check the depth of water in the sump.
Colleagues working nearby heard Mr Benn's shouts, but when they got to the sump he had disappeared from view, the HSE said.
Epsco Ltd pleaded guilty in court to a charge under Section 2 (1) of the Health and Safety at Work etc Act 1974.
It was fined £35,000 and ordered to pay costs of £120,000.
HSE principal inspector Colin Mew said he hoped other employers would learn from the mistakes made by Epsco Ltd.
"This incident was entirely foreseeable and yet it was still allowed to happen," he said.
"Epsco Ltd would have known Mr Benn or one of his colleagues would need to approach the sump in the course of their work.
"The inherent risk of working in this manner should have been obvious to any diligent employer.
"This company failed to put a safe system of work into place. The enclosed area where this work was taking place was poorly lit, noisy and conditions were wet and slippery.
"The cost of providing barriers or other measures to prevent this incident and the time and effort involved would have been minimal."
He added: "The real tragedy here is the human cost that has resulted from the death of Michael Benn and the ease with which his death could have been prevented - I hope that other employers take heed of this message."
Epsco Ltd said it would not be commenting on the case.