Two companies which admitted breaching health and safety rules after two welders died in a ballast tank are due to be sentenced on Friday.
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 at Ipswich Crown Court.
Tank owners Edmund Nuttall admitted failing to ensure the men's safety.
The court heard from the Health and Safety Executive that the way the work had been carried out was "na´ve".
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.
Thursday's hearing was told there had been verbal warnings about the dangers of the work, but there had been no written assessment of the risks.
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.