Although most of us spend our lives as landlubbers, we live on an ocean world. Just 29 percent of Earth’s crust rises above the water’s surface today. During the Archean eon—the planet’s tumultuous toddlerhood—almost nothing did. With some 8.3 billion of a certain kind of poorly-adapted mammal on board, it’s only a matter of time before one of us has an unfortunate run-in with those vast stretches of watery nothingness.
And in those moments, survival rests on circumstance, preparation, and a lot of luck.
This was certainly the case earlier this month when the Hellenic Coast Guard successfully rescued a 44-year-old El Salvadoran woman who jumped off a Royal Caribbean cruise ship because she “wanted to disembark” (you have to admire the confidence). The woman creatively “disembarked” from the Odyssey of the Seas around 10:30 a.m. local time while sailing through the Ionian Sea along Greece’s western coast. Twenty hours later, she was spotted bobbing along in a bright orange lifebuoy by a cargo ship assisting the search-and-rescue operation.
Despite what Hollywood would have you believe, a person’s immediate threat on the open water is not other animals. The ocean is so massive that the odds of a run-in with a predator is vanishingly thin, and even if such an encounter occurred, humans are not natural prey for these animals. As long as you limit thrashing to a minimum (a good idea in order to conserve energy while also not triggering a prey response), it’s unlikely you’ll wind up as dinner for some sharp-toothed monster of the deep.
Instead, survivalists often say that a person’s top four priorities when adrift at sea are securing freshwater, shelter, food, and a signaling device. In this particular instance, the woman’s saving grace was her bright orange lifebuoy, which helped her stand out, even at night, among the Mediterranean’s endlessly undulating waves. Without it, exposure and dehydration would have killed her.
Some have drifted for months, even years. The difference is that they usually go into the water with a vessel, supplies, or tools—unlike someone who simply goes overboard. In August, the Mexican Navy pulled two fishermen from the Pacific roughly 150 miles off Chiapas, where they’d spent five days floating in a cooler box after a wave sank their boat. They survived on nothing at all—no food, no water—which is precisely why five days was close to their limit. Longer ordeals demand more than endurance, and past instances of other daring feats of open ocean survival can provide some clues about what that entails.
For example, a little over a decade ago, Jose Alvarenga drifted in the open ocean for more than a year. He secured freshwater by devising ways of trapping rainwater, and when storms proved scarce, he relied on drinking the blood of turtles captured by hand. Duke University medical specialist Claude Piantadosi, speaking with National Geographic after Alvarenga’s shocking rescue in 2014, said turtles likely helped the adrift survivor stave off another well-known illness that’s plagued seafarers for millennia.
“The availability of fresh turtle or bird meat—for example, the liver—would have prevented him from getting scurvy,” he said. “Blood from birds and turtles is a good source of water—70 percent water—and has no more salt than human plasma.”
Piantadosi also mentioned that drinking urine can offer a method of last resort, since you’re re-ingesting salt already eliminated by your kidneys. This fact also points to why you can’t just drink the endless seawater around you to stay hydrated. According to NOAA, human kidneys can only make urine less salty than salt water, so it’d take even more freshwater to get rid of the excess salt, making you more thirsty and dehydrated in the process.
So if you find yourself adrift in the open ocean, not all hope is lost. Secure a source of freshwater, provide shelter from the sun, limit activity to store energy, and signal to passing ships and aircraft if possible. With some forethought—and a little bit of luck—you’ll come out the other side a survivor.
Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.