Swimmers sometimes complain that water can be “evil,” but water is water, right? Wrong. So-called dead water—a naval phenomenon that happens when waves form between layers of warmer and cooler water, reducing a ship’s speed—may affect swimmers too, the New Scientist reports. And it might be what’s behind the otherwise-mysterious drownings of seasoned swimmers.
Scientists ran experiments that compared swimming in normal water to dead water, and concluded that energy and speed dropped in the latter. “We’ve been considering the possibility that the drownings of strong swimmers in fair-weather conditions might be the result of dead water, but until now, we weren’t really sure if this phenomenon could strike something as small as a single human,” one says.