Vincent Valinducq explained on French television show Bonjour ! La Matinale TF1 that the sudden urge to urinate when entering cool pool or sea water is driven by a natural physiological reflex. Responding to a viewer question on the broadcast, he detailed how the human body reacts automatically whenever it is immersed in water that is colder than normal body temperature.
When a swimmer steps into cool water, the blood vessels in the skin constrict immediately to reduce heat loss. This automatic process, known as vasoconstriction, redirects blood away from the skin surface and towards vital internal organs such as the heart and the brain.
Because of this sudden internal shift in blood distribution, the body interprets the increased central blood volume as an excess of fluid in the system. To restore internal balance, the body signals the kidneys to filter out the perceived surplus fluid, which leads directly to the rapid production of urine and a pressing urge to relieve oneself.
How Vasoconstriction and Kidneys Regulate Fluid
Valinducq stressed during the morning broadcast that this sudden urge is a completely normal response rather than a sign of any medical abnormality. The reaction occurs almost instantly after dipping into a swimming pool or the sea, affecting nearly everyone who enters cooler water.
Human body temperature is typically maintained around 37 degrees Celsius, whereas sea and pool waters are generally significantly cooler. Vasoconstriction is a well established vascular mechanism where smooth muscles in blood vessel walls contract, helping the body preserve core warmth during cold exposure.
The kidneys function as the primary filtration system of the human body, removing waste products and managing fluid levels to maintain homeostasis. When central blood pressure and fluid volume rise during cold immersion, the kidneys increase urine output to keep systemic blood volume within safe limits.
Everyday Physiological Reactions Explained on TF1
Bonjour ! La Matinale TF1 is a morning news program broadcast nationally in France on the TF1 network. For viewers seeking additional information about this physiological reflex and other everyday physical reactions, a full video segment featuring Valinducq provides accessible and detailed explanations.
