The belief:

“If go swimming after you eat, you’ll drown.”

The informant doesn’t remember where he heard this rumor, but he thinks it was probably from a friend’s mother during his childhood. He doesn’t think it’s true now, though. In my opinion, I think this is a popular statement told to children by their parents so that they let their food digest before they get back in the water to swim. Another popular belief is that you’ll get cramps if you swim right after eating, so maybe the parents who say this more extreme belief are just trying to protect their children from painful cramps.