Two firms have been fined a total of £125,000 after two welders died as they tried to dismantle a ballast tank.
Charles Buckenham died trying to save his step-father
Charles Buckenham, 52, of Lowestoft, and his stepfather Brian Dove, 55, from Burgh Castle, Norfolk, were overcome by fumes in the tank at Lowestoft in 2003.
Their employers, Small and Co Marine Engineering, admitted failing to ensure their safety and were fined £100,000.
Tank owners Edmund Nuttall were also fined £25,000 at Ipswich Crown Court for breaching safety rules.
The company had admitted failing to ensure the safety of people who were not its employees.
Both firms were ordered to pay £29,500 costs between them.
The court heard Mr Dove had not received any specialist training about working in confined spaces, and Mr Buckenham had received no training at all.
Judge John Holt said the risks to which the men were exposed to were "totally forseeable", and he extended his sympathies to the men's families.
The men had been sent to examine the tank to establish the best way of disposing of it.
At some point Mr Dove ended up inside the tank. Mr Buckenham went into the tank to try to rescue him and both were overcome by fumes.
Emergency services took seven hours to retrieve the men's bodies from the five metre by 15 metre tank because the search was hampered by water and slurry.