@Aoitenshi It's not really an issue. There haven't been any recorded cases of someone drowning because they ate too much before swimming and although they typically don't completely stuff their stomachs full, swimming athletes regularly eat before swimming.
If you eat a lot and do some very heavy swimming, like participating in an actual swimming competition, straight after eating, you might at most get a very minor stomach cramp or feeling a bit nauseous and even that would be extremely rare, plus the same is true for any heavy exercise performed right after a very big meal and most people at the pool typically don't do any heavy swimming either way. What's more, even an actual strong cramp wouldn't be enough to cause someone who knows how to swim, to drown.
The only things people have ingested before swimming that are known to pose a big risk of drowning, are things like drugs and alcohol. There have been many cases of people drowning while drunk.