When a crime occurs on water, the jurisdiction depends on how far it is from land. In international waters, more than 24 miles off the coast, the crime would fall under the laws of the country where the ship is registered. If a ship is at port when a crime occurs, it falls within that country's jurisdiction.

Laws on cruise ships are a complex blend of the "Flag State" laws and the laws of the Territorial Waters they are in. While in port or within 12 nautical miles of a coast, the ship must obey the local laws of that country (e.g., gambling and drinking ages might change). Once in International Waters (High Seas), the laws of the country where the ship is registered (the Flag State, such as the Bahamas, Panama, or Bermuda) generally apply. This covers everything from labor rights to criminal proceedings. However, if a crime involves a U.S. citizen, the FBI often has jurisdiction under the Cruise Vessel Security and Safety Act. Additionally, cruise lines have their own "Guest Conduct Policies" which can result in you being "offloaded" (forced to leave) at the next port for disruptive behavior, even if no local or international law was technically broken.