Urgent action is needed to tackle excessive working hours at sea, a UK maritime trade union says.
The report calls for better reporting of working hours at sea
The comments by the Nautilus union came after a survey of 1,800 seafarers found that almost half of respondents had working weeks in excess of 85 hours.
Half of those who took part in the study also agreed their working hours were a danger to their personal safety.
A further 37% said excessive working hours posed a danger to the safe operations of their ship.
The six-year study was co-sponsored by the Maritime & Coastguard Agency and the Health & Safety Executive, with support from Nautilus and the Seafarers' International Research Centre at Cardiff University.
It concludes that working hours at sea need to be much better recorded.
"This proves conclusively the serious nature of the problem and the massive scale to which fatigue is suffered by seafarers," said Nautilus UK general secretary Brian Orrell.