There are enough people saying this on here that I have to believe it ' s actually something that people are taught , but man , does it seem ridiculous . I mean , I ' m far from an expert on swimming , lifeguarding , punching or head trauma , but it just seems like a terrible idea all around . 1 . First , you have to get close enough to punch them , which means you are close enough for them to grab your arm . You are now within grappling range of a person who was already flailing for their lives , and is now also faced with the additional terror that the person who ostensibly was coming out to help them has surprisingly decided to beat them up instead . I ' m now picturing a person punching out a drowning victim while yelling I ' m a friend , I ' m here to help you ! , like the aliens in Mars Attacks . 2 . The punch . You are swimming , not standing on stable ground . Also , your arm is going to be at least partially in the water as it travels . This isn ' t going to be one of the alltime greatest punches . Also , the only part of the person exposed is their skull , so you ' re aiming an awkward , impeded punch at the part of the body most likely to result in bruisedbroken knuckles , which probably isn ' t going to help your focus during the rest of the rescue . 3 . If you do manage to land one or more blows solid enough to knock them out , my understanding is that this can also be a very dangerous thing medicalwise . Now you have a person with water in their lungs , and a possible concussion . Maybe this still gives them better odds than just letting them exhaust themselves and possibly drown beyond recovery , but I ' d be curious to see the numbers on it . I suppose if nothing else , anyone seeing this happen in person is probably going to move those swimming lessons up on their list of things to do PDQ .