Executives of Carnival Corp., Norwegian Cruise Line and Royal Caribbean Cruises told the committee during a hearing Wednesday they would report all alleged crimes that occur on their vessels.

In a prepared statement, Rockefeller expressed skepticism about the cruise lines' pledge.

"I have been assured repeatedly by the industry that things will get better," he said. "Take a look at the events over the past 16 months and tell me if this is what you think better looks like. Cruise lines are on notice that the safety and protection of passengers is now their number one priority, whether they like it or not."

The cruise lines voluntarily agreed to post reports of alleged crimes reported as far back as 2010 on their website by Aug. 1 regardless of whether an investigation is open or closed.

A statement on Carnival's website says the possibility of a criminal incident aboard their ships is "remote." Of the 4 million passengers the cruise line expects to carry in 2013, the website says, "the number of alleged incidents is a small fraction of those carried."