When I lived on a small and shallow river I couldn't take swimming lessons at the beach because I'd heard sharks could swim up rivers. My mother tried to tell me in vain that they meant rivers like the Amazon, but we were only like twenty minutes from the ocean and I live in NorCal, home of allll the great whites.

Also, when I was a little girl I saw the beginning of a movie where a woman was swimming in the 12' end of a pool, and someone swam near her and handcuffed her foot to the drain and she drowned. Talk about lifelong scarring.