When I was younger I used to believe that sharks lived in any body of water (including swimming pools). So everytime I jumped off the edge or the diving board I would swim as fast as I can to get back out because I thought a shark would come out of the pool wall and eat me.
A childhood belief about swimming pools

others believed things like this
- I used to think that a "pool shark" was an actual shark that lived in a swimming poolAnon
- i used to believe that pools had underwater doors that sharks were going to swim out of.— marky
- I used to believe that sharks lived under the pools where the air vents were. — Carol
- I used to believe that if you farted while swimming in the pool, it could propel you foward really fast.— Rick
- When i was younger,I used to believe i could see a shark in a pool .Anon
- I believed that the ladder on the back of a trailer/rv led up to a swimming pool.— marilese