"The captain goes down with the ship" is a line that any seafaring person, or movie buff, would be familiar with. It's the idea that a sea captain holds ultimate responsibility for not only his ship, but everyone on board and will go down with it if that's what it takes.

For many, the iconic scene  in "Titanic" of Capt. Edward Smith's heroic demise on the bridge was the introduction to the maritime concept. (Paramount Pictures / "The Titanic")

But, unsurprisingly, reality rarely lives up to the silver screen. The captains of Italy's Costa Concordia in 2012 and more recently the South Korean Sewol ferry were far from the last to disembark their ships before they capsized. (Via YouTube / Team BlacksheepVoice of America)

And this isn't a new thing. In 1991 the captain of the Greek cruise liner Oceanos was lambasted after abandoning ship. (Via ABC)

Which brings us to the question: just how serious is the tradition that the captain goes down with his ship?

The modern U.S. code, according to a professor at Florida's Coastal School of Law interviewed byNPR, states that the captain is "legally required to render assistance to every single person trying to get off that ship, and also identify those people who may have been killed in the incident."

ABC notes that while there aren't any international maritime laws requiring a captain to stay with his sinking ship, "many countries either have their own laws or subscribe to international treaties that mandate certain behavior."

One such international treaty is the Safety of Life at Sea convention handled by the International Maritime Organization, which has been signed by both Italy and South Korea. The convention requires that passenger ships have emergency management systems in place. (Via United Nations)

Speaking with the BBC, a former Swedish master mariner noted an unspoken rule: that the captain is to stay on board the ship to direct evacuation in the case of an emergency.

"How would a captain fulfill his obligations if he was not on board? Emergency responses are nearly almost always coordinated from the ship - you have fairly limited options for getting necessary information from a lifeboat."

The New York Times points out it's a complicated code of conduct though, saying that while civil courts in the U.S. have long seen captains as responsible for their crew, "the cases in South Korea and Italy seem likely to test the notion of criminal liability in disasters."

Both captains of the South Korean ferry and Italian cruiseliner are facing criminal charges. But while Francesco Schettino of the Concordia is on trial for manslaughter, Lee Jun-seok is only facing charges for negligence of duty and violation of maritime law.