We all know what it looks like when someone is drowning, right? Profuse flailing, spewing water, waving arms and yells for help...

And we all have it wrong.

In one of the more chilling statistics to come from the Centers for Disease Control and Prevention, Slate.com reports that of the approximately 750 children who will drown next year, some 375 of them will do so within 25 yards of a parent or another adult. In 10 percent of those drownings, the adult will actually be watching the child and have no idea that he's in trouble.

Despite the signs of drowning that we know so well from film and television, in reality, there is little drama. Because of the “Instinctive Drowning Response,” a term coined by Francesco A. Pia, Ph.D., people who are drowning become very quiet and do not wave for help.

So how are we supposed to know?

In an article from the Coast Guard’s On Scene magazine, Pia and aviation survival technician Mario Vittonelists list the characteristics of the Instinctive Drowning Response:

1. Except in rare circumstances, drowning people are physiologically unable to call out for help. The respiratory system was designed for breathing. Speech is the secondary or overlaid function. Breathing must be fulfilled before speech occurs. 2. Drowning people’s mouths alternately sink below and reappear above the surface of the water. The mouths of drowning people are not above the surface of the water long enough for them to exhale, inhale, and call out for help. When the drowning people’s mouths are above the surface, they exhale and inhale quickly as their mouths start to sink below the surface of the water.
3. Drowning people cannot wave for help. Nature instinctively forces them to extend their arms laterally and press down on the water’s surface. Pressing down on the surface of the water permits drowning people to leverage their bodies so they can lift their mouths out of the water to breathe.
4. Throughout the Instinctive Drowning Response, drowning people cannot voluntarily control their arm movements. Physiologically, drowning people who are struggling on the surface of the water cannot stop drowning and perform voluntary movements such as waving for help, moving toward a rescuer, or reaching out for a piece of rescue equipment.
5. From beginning to end of the Instinctive Drowning Response, people’s bodies remain upright in the water, with no evidence of a supporting kick. Unless rescued by a trained lifeguard, these drowning people can only struggle on the surface of the water from 20 to 60 seconds before submersion occurs.
Which isn’t to say that someone flailing about isn’t in need of help — they might be in the throes of “aquatic distress,” which may or may not be present before the Instinctive Drowning Response kicks in, but aquatic distress doesn’t last long.

Reader’s Digest reminds us that sometimes the most important indicator that someone is drowning is that they don’t look like they’re drowning. If you notice any of the signs listed above, ask the swimmer if they are all right. The magazine also notes, “children playing in the water make noise. When they get quiet, you need to get to them and find out why.”

You can see the Instinctive Drowning Response in the video below. (And don’t worry, the swimmer is rescued in the end.)

Related swimming stories on MNN:

The seriously surprising signs of drowning
Forget what you thought you knew about drowning; it looks nothing like most of us think. Here’s what to watch out for.