A childhood belief about swimming pools

when i was little and we went on holiday. i used to be a complete pool baby and i wouldn't get out of the pool. so when i needed the loo i'd just go to the loo in the pool. i know it's disgusting but so was the toilet.
anyway my mum found out and then said calmly to me: "sarah,if you wee in the pool you'll get a purple ring around you when you swim"
i believed her for ages and never did it again.