There is an old saying that it is good to wait at least for 30 to 45 minutes before swimming, after havig a big meal. This saying depends on the idea that after you have eaten a big meal, your body’s blood will be more inclined to flow towards your digestive area instead of your arms and legs. So if your limbs do not have enough oxygen, you might end up downing.
However, this is not true at all. In fact, we do always have just enough blood flowing in all parts of our bodies to function properly. Nevertheless, there can always be an uncomfortable feeling when you do some rigorous exercise right after a meal. This can cause vomiting or reflux of the stomach contents.