Humans have been scared of sharks as long as we've known how to swim. Though the data doesn't quite back up our phobia (you're more likely to be struck by lightning than injured by a shark), the sight of all those sharp teeth activates something deep within our animal psyche that tells us to RUN. AWAY. NOW.
YouTuber Jay Karl knows this better than most. In a recent prank, he drove a motorized shark fin toward swimmers at a local beach and the reactions are memorable.