Before swimming lessons, my mom would always tell me to finish eating ALL of my lunch, and that if I didn't...in the water, I'd sink - because I didn't have enough food in me.
I honestly believed this till about grade 7...in what turned out to be an embarassing conversation with friends.
A childhood belief about swimming pools

others believed things like this
- When asked why he didn't finish eating the crust from his pizza, a young friend said "I don't eat the bone".— Dustin
- If you eat 30 minutes before swimming, you will sink.Anon
- Up until I was in 3rd grade I believed my bathing cap is what kept me afloat in the swimming pool! Anon
- A[n] nth grade teacher only had to finish the nth grade when he or she was in school.— MD Caruso
- You had to wait an hour after eating ANYTHING, even one M&M, before swimming. Anon
- I didn't think you could put out a fire with hot water - only cold water would do.— Katti Pytt