Traveling via cruise ships is one of the more popular vacations options, especially for Americans. One report from Travel Agent Central claims that in 2016 alone, more than 24 million people from the US took a cruise traveling to ports from Alaska, Nova Scotia, Key West, and Cozumel. While serious crimes aboard ships are relatively rare, it isn’t unheard of, and due to confusing and unclear jurisdictions, many cruisers are unaware that after a ship leaves the 12 mile limit past the US coastline, they are no longer protected by US law.

“Past 12 nautical miles from shore, passengers are subject to the laws of whatever country a ship is flagged under,” explains Martin Davies, director of Tulane University’s Maritime Law Center in New Orleans, Louisiana. “Most cruise ships leaving from American ports are not flagged in the United States; instead, cruise lines use the ‘flag of convenience’ system, and most of the vessels are registered in countries like the Bahamas, Bermuda, and Panama.”

When a crime occurs on board, the flag country has “first dibs” at investigating and prosecuting crimes, regardless of where the victim and the suspect originated. The problem is that many of these countries are unwilling or unable to investigate, and thus many times the ship’s captain (legally called the ship’s master) doesn’t bother reporting the crime to the flag country. If the master decides that his vessel’s flag country is not equipped to investigate the matter, he or she may choose to report the crime at the ship’s next port of call. For example, if a passenger was caught with drugs onboard while the ship is steaming to Cozumel, the master may hand the person over to Mexican authorities once the ship docks. If the crime occurs within 12 miles from any coastline, he may also choose to report the crime there, but given the ship’s large size and tight itinerary, this is rare.

However, there is no guarantee law enforcement in port will be interested in the case. If this happens, the ship’s master has only one choice left: report the crime once the ship docks at its home port back in the United States. The master can report the incident to local law enforcement or refer the case to the Federal Bureau of Investigation. Even this option is mostly futile, as suspects are likely to flee the port as soon as the ship docks, and with the ship’s intense schedule it’s almost impossible to collect evidence, examine the crime scene, or interview suspects.

“Most of these cases are never tried in a criminal court,” says Davies. “Passengers’ best option is to sue the cruise line in civil court. The cruise line is likely to settle out of court if the crime is minor, but the company will usually go to trial if the incident is serious enough.”

As for the suspects, Davies says that the majority of the time they walk away without consequences. The victim will likely receive a small settlement from the cruise line, but past that there aren’t a lot of options left. Davies also strongly encourages passengers to read their ticket and understand their liability once they set sail.