As a kid, you were probably told that you must wait a half hour after eating to swim, or risk cramping up and drowning, or something similar. But it turns out this is nothing more than a myth. Back in 1918 a publication called How to Swim, said that "a period of at least two hours should elapse between eating and entering the water" because if the water's cold it could stop the digestive process and start severe cramping. Modern science hasn't been able to confirm this, and competitive swimmers actually eat before and during long distance swims.