Since 2011, 959 cruise ship crimes were reported to the FBI, but only 31 were published to a website maintained by the U.S. Coast Guard.
The disparity comes from the fact that the site only publishes incidents that are no longer under investigation, potentially misleading the public about the risks aboard cruise ships.
In 2007, cruise lines agreed to voluntarily report "serious" violations of U.S. law to the FBI, including accusations of homicide, sexual assault, suspicious death, and kidnapping.
In 2010, Congress ordered the Coast Guard to maintain a website with a statistical record of alleged crimes, but only closed cases have been published.
"Under current law, cruise ship crime report data is not available to the public," said Sen. Jay Rockefeller, chairman of the Senate Commerce Committee. "That means consumers have no way to find out what their real risks are before they book a cruise."
The West Virginia Democrat released the statistics on Wednesday ahead of a hearing on safety and security on cruise ships.
Industry representatives say crime is rare. Carnival and Royal Caribbean, two of the largest cruise lines, reported a combined seven incidents in the quarter ending June 30 -- all sexual assault or assault involving serious bodily injury.
On its website, Carnival emphasizes that 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."
But Rockefeller has introduced legislation that would put the Department of Transportation in charge of cruise ship consumer protection, would require the industry to disclose all crime alleged on ships and would require increased video surveillance on ships.
"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," Rockefeller said. "You can only call the ship's security officers, who also happen to be employees of the cruise line."