Washington (CNN) -- Vegas stole the slogan. But cruise ships can also lay claim: Whatever happens on cruise ships, stays on cruise ships.
Only a tiny portion of alleged crimes on cruise ships is ever publicly disclosed, according to a report by the Senate Commerce Committee.
Of 959 crimes reported to the FBI since 2011, only 31 were disclosed on a web site maintained by the U.S. Coast Guard.
As a consequence, passengers have an incomplete picture of crime on board of ships.
Sen. Jay Rockefeller, a West Virginia Democrat, disclosed the statistics on Wednesday in advance of a hearing on safety and security on cruise ships.
"I've been told time and again that cruise lines will change, that things will get better for passengers," Rockefeller said in a statement. "But according to our investigation, it doesn't appear to me that passengers are substantially safer."
In 2007, the FBI, Coast Guard and the cruise lines agreed that the industry would voluntarily report to the FBI incidents involving serious violations of U.S. law, including homicide, suspicious death, missing U.S. nationals, kidnapping, assault with bodily injury, sexual assaults, firing or tampering with vessels, and theft greater than $10,000.
Three years later, Congress ordered the Coast Guard to maintain a web-based statistical record of alleged crimes.
But the site discloses only incidents no longer under investigation, giving the public an incomplete picture, Rockefeller said.
Rockefeller has introduced legislation that would require industry to disclose all crime alleged on cruise ships, and beef up video surveillance of public areas.
It also would give the Department of Transportation the lead agency for cruise ship consumer protection, akin to its role in aviation.
Crime on cruise ships, though infrequent, presents special problems, Rockefeller said.
"If someone steals your property or assaults you on a cruise ship, you cannot call 911 and have the police there in a few minutes. You can only call the ship's security officers, who also happen to be employees of the cruise line," he said in written remarks.
"Under current law, cruise ship crime report data is not available to the public. That means consumers have no way to find out what their real risks are before they book a cruise."
The industry emphasizes that crimes are infrequent.
For instance, two big cruise companies, Carnival and Royal Caribbean, reported a combined seven incidents in the quarter ending June 30. All were either assaults involving serious bodily injury or sexual assaults.
"There is nothing more important to us than the safety of our guests," Carnival says on its web site. "Public reporting requirements ... are unique to the cruise industry and similar requirements do not exist for other travel suppliers such as airlines, hotels and theme parks."
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