Passengers on cruise ships run nearly double the risk of being sexually assaulted that they do in normal life, a researcher claims.
Professor Ross Klein told a conference at the Auckland University of Technology that cruise liners were not as safe as most people assumed, and crew members were overwhelmingly to blame for most rapes and assaults.
Professor Klein, from Memorial University in Newfoundland, Canada, said the cruise ship industry, which has expanded hugely in recent years, had tried to cover up incidences of rape and sexual assault to avoid negative publicity.
He studied figures submitted to the US Congress by the industry last year and found that the rate of sexual assault on cruise ships was 59 per 100,000 compared with a norm in the US of 32 per 100,000.
There were an additional 53 cases per 100,000 of sexual harassment.
Nearly 70 per cent of sexual assaults were carried out by crew on guests, and 10 per cent by crew against fellow crew members.
The reasons for the higher incidence of sexual assault on ships included the easy availability of alcohol, passengers letting down their guard and the predatory behaviour of some onboard staff.
"People are on holiday so they don't think about the dangers," said Professor Klein, a sociologist who has written three critical books on the cruise industry.
"On some ships you have crew members organising contests between themselves to see how many passengers they can sleep with. The younger the passenger, the more points they score."
The number of sexual assaults and rapes varied dramatically from ship to ship, with fewer incidents on more expensive cruises, where the clientele are older.
"Senior officers have told me there are different cultures on different ships," said Professor Klein, who has been blacklisted by some cruise companies because of his research.
The Seattle-based International Cruise Victims Organisation, formed by several families with similar cruise ship horror stories, lists dozens of alleged crimes at sea, including the disappearance of 18 people.
The organisation says many assaults go unreported because passengers "often feel alone and frustrated by jurisdictional uncertainties and poor treatment by cruise companies".