On March 23  the Ever Given, a ship the length of the Empire State Building, ran aground in the Suez Canal, causing a traffic jam of epic proportions in one of the busiest shipping routes on the planet. When it did this, it revealed a $20 trillion sector of the worldwide economy that otherwise functions behind the scenes.

The Ever Given was freed after six days, but Lawrence Brennan, a retired U.S. Navy Captain who served aboard the USS Nimitz aircraft carrier and now teaches admiralty and international maritime law at Fordham Law, said the snafu illustrates just how dependent we are on a system we often take for granted—one that has real vulnerabilities worth considering.