SUEZ, Egypt—Chief Mate Mohammad Aisha awoke to the groans and tremors of a cavernous cargo ship listing hard to starboard. He staggered through the darkness up five flights of stairs to the bridge and shined his phone’s flashlight on the navigation dials.

The MV Aman was tilting 10 degrees, its 330-foot-long hull taking on more than 6 feet of water. Three miles from the nearest ship, Mr. Aisha knew that if the 3,000-ton boat went under, it would suck him, the only person on board, into the Red Sea.

This was a crisis. It was also Mr. Aisha’s best chance to escape.

For months, the 29-year-old Syrian had been the last sailor still living on a cargo ship, abandoned two years earlier near the mouth of the Suez Canal and being detained by the Egyptian government. They had refused to let him disembark but couldn’t keep him on the ship if it was sinking, he reasoned.

He activated an emergency beacon and shouted “Mayday! Mayday!” into the radio. Hours crawled by before a military patrol arrived to whisk him to land.