Indonesian Teen's Secret to Surviving 49 Days at Sea Is Filter Science 101

He found a brilliant way to drink salty seawater.

For 49 days, Aldi Novel Adilang was stranded in the Pacific Ocean. The Indonesian 18-year-old, whose job is to maintain a wooden fishing hut off the nation’s coast, became stranded in mid-July when heavy winds unmoored his floating fish trap. Adilang ended up hundreds of miles away, near Guam, where his emergency signal caught the attention of a Panamanian vessel. His survival has been chalked up to extreme ingenuity, and a bit of luck.

On Monday, The Jakarta Post reported that Adilang survived by catching fish and burning the parts of the floating hut, called a “rompong,” to make fire for cooking. To stave off thirst, Adilang relied on one of the few things he had: his shirt. According to Indonesia’s Consul General Mirza Nurhidayat, Adilang “drank by sipping water from his clothes that had been wetted by sea water.”

This may seem impossible: After all, seawater is so salty that it’s toxic to the human body. The body can get rid of excess salt through its kidneys, but if a person doesn’t consume fresh water during that process, then all that salt doesn’t undergo the dilution necessary to excrete it. According to the National Ocean Service, a person would have to urinate more water than they drink to get rid of all the salt consumed in seawater. Eventually, this process leads to death by dehydration.

Nurhidayat’s quote seems to be the only evidence that Adilang used his clothes as a means to drink water, but some outlets are reporting that the soon-to-be 19-year-old used his shirt as a filter. And that, according to some scientists, might actually work.

Two studies have shown that filtering water through a sari — a garment commonly worn by women in the Indian subcontinent — can significantly increase its potability. In 2003, scientists discovered that filtering water from rivers and ponds in Bangladesh through a folded piece of cotton cloth taken from a sari cut the risk of infection with cholera by half. Interestingly, they noted that old cloth makes for a better filter than new cloth because the pore size of loose threads is smaller.

In a follow-up study in 2015, researchers found that a filter made of four layers of worn cotton material could filter out more than 99 percent of all cholera bacteria.

You might also like this video explaining how scientists are developing water filters for villages in Bangladesh.

While boiling water is still considered a better way to purify water, scientists still consider the cloth technique to be uniquely useful. But whether cloth do the same thing for salt as it does for bacteria is debatable. Some YouTube survivalists say it can, but others recommend another cloth-meets-saltwater method: A CNN guide to being stranded at sea recommends using the shirt to capture moisture from the air and then wringing it out.

Using cloth as a filter likely wouldn’t remove all the salt from seawater, but it could certainly reduce salt levels to less dangerous concentrations. According to the United States Geological Survey, fresh water typically has a saline concentration of 1,000 parts per million (ppm). In comparison, ocean water contains 35,000 ppm of salt. It entirely possible that Adilang’s clothes removed enough salt molecules from the water that his kidneys could process it without becoming dehydrated.

If you ever find yourself adrift and have access to the materials, the more frequently recommended method of saltwater purification is distillation. In its most basic form, distillation could mean boiling seawater in a pan and capturing the steam as it condenses on a surface, like a plastic soda bottle. The resulting water should be largely salt-free. It’s a slow process, sure, but it could also mean the difference between life or death.