“Don’t go swimming right after eating! Wait 30 minutes to go into the water. You’ll get cramps and drown!” The theory was that after you eat the blood rushes to your stomach to digest your food and leaves the muscles unattended. Without a good blood supply the muscles cramp, you can’t move your limbs, and so drown. In the 1960’s this belief was put to the test. Swimmers were fed hearty breakfasts and then asked to swim at various times afterward. Researchers found no cramping in any of the swimmers. Waiting to swim after eating is not required! Don’t listen to Mom!
See and read more at: https://www.livescience.com/eating-before-swimming.html