You should wait several hours after a meal before swimming to avoid hydrocution.

noli's read

The idea that a large meal automatically causes hydrocution when swimming is a widely debated popular belief. Current scientific research indicates that digestion does not divert enough blood from the muscles or brain to cause syncope during moderate aquatic activity. Hydrocution is actually a sudden thermal shock linked to a significant difference between body temperature and water temperature, rather than digestion. According to available data (expert opinion in first aid and physiology), the major risk remains entering cold water too quickly, regardless of stomach content. It is therefore recommended to enter the water gradually to acclimate the body, rather than focusing solely on the delay after a meal. This traditional recommendation is therefore considered an oversimplification of a more comprehensive safety mechanism.

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