Drowning, in real life, doesn't look or sound the way it does on TV. It's not loud. It's not thrashy. And it can happen just a few feet away from you without you even noticing. At Slate, Mario Vittone explains the Instinctive Drowning Response — a physiological knee-jerk reaction that pretty much prevents all the signs and signals most of us look for in order to identify a person in the water who needs help.