Screenshot from the YouTube channel theCHAIZYchannel
Before watching the video I really thought it would be one of those crappy prank where a douche just piss of people, and yet this time it's only is a little bit of that.

Putting shampoo on people's head would just be rude, but in this video the pranksters from theCHAIZYchannel just add shampoo on people that are already washing their hair on the beach. What happens is that the victims just can't get rid of the shampoo from their hair has the guy keeps discretely adding more.