Family members of those who have disappeared on cruises will testify before Congress Tuesday in an attempt to get some answers about their missing loved ones.

Over the past five years, the FBI has opened more than 300 cases relating to crime on the high seas. While most crimes committed on cruise ships consisted of sexual and physical assaults, some passengers simply vanished, never to be seen again.

Over a three-year period, 28 people went missing on cruises, according to a memo prepared for the House subcommittee that will hold the hearing. Only five of those people were recovered or found.

Several families of the missing say the cruise lines did not thoroughly investigate disappearances, and in some cases, families have accused cruise officials of witholding information or cover-ups.

Families Still Waiting

One of those still missing is George Smith, who disappeared from Royal Caribbean Cruise Line's Brilliance of the Sea while traveling between Greece and Turkey last year. The 26-year-old lawyer from Greenwich, Conn., was on his honeymoon with his wife, Jennifer.

Among those testifying at the hearing will be Kendall Carver, of Phoenix, whose 40-year-old daughter, Merrian, disappeared from the Celebrity Cruise Line ship Mercury during an Alaskan cruise in 2004. Officials of Celebrity, a subsidiary of Royal Caribbean, investigated the disappearance and reported back to the parents that they thought their daughter had committed suicide.

The Carvers were not satisfied with that answer and asked how a determination could be made when no body had been found. They subsequently sued the cruise ship company.

Other witnesses will testify that they were sexually assaulted and robbed during cruises.

"A business built on the premise of pleasure-filled conveyance has little incentive to inform third parties when the trip goes wrong," said Rep. Christopher Shays, R-Conn., who will chair the hearing. He wants to examine the effectiveness of procedures governing maritime security, passenger security and the thoroughness of investigations of shipboard incidents.

Officials of Royal Caribbean International and Holland America Lines are also scheduled to testify.