Summer holidays by the sea are often associated with heat and the desire to dive into refreshing waves. However, as experts note, beach leisure can turn into a serious test for the body if the physics of the process are not understood. The Ukrainian Hydrometeorological Center (UkrGMC) has explained to residents why water may feel different at different times of the day and warned about hidden health risks.

The Physics of Sensation: Why Water "Cools Down" During the Day

Many vacationers face a paradoxical situation: in the morning, the water seems comfortable, but by midday, when it gets hotter outside, it feels icy. Employees of the Hydrometeorological Center of the Black and Azov Seas in Odesa explained that the issue is not the actual water temperature, but the laws of physics and human physiology.

Experts emphasize: a person does not perceive the temperature of the environment itself, but the rate at which their body loses heat. Since human body temperature is usually higher than the ambient temperature, thermal conductivity—the ability of a substance to conduct heat—plays a key role.

Water has significantly greater density and thermal conductivity than air. This is why it draws heat from the body much more efficiently. In air, heat is transferred by convection (air currents), whereas water, due to its high density, instantly "takes" heat from the skin.

The Role of Solar Heating and Temperature Contrast

In the morning, when the sun has not yet reached peak activity, the air temperature on the beach and the water temperature are often close to each other. At night, the air cools faster than the water, which retains the heat accumulated during the previous day. Therefore, morning swimming seems more comfortable.

The situation changes as the sun rises. The Earth's surface and the air heat up actively, and human skin under direct rays also increases its temperature. Water, however, heats up significantly slower. As a result, a strong contrast arises between the temperature of the heated skin and the cool water.

"The greater the difference between the surface temperature of the body and the water, the higher the heat loss and the stronger the person feels the cold," they note at UkrGMC.

Medical Aspect: Stress for Blood Vessels

In addition to physical laws, experts drew attention to the body's reaction. When the skin heats up, blood vessels dilate, and breathing deepens, which promotes natural cooling. However, a sudden plunge into cool water causes the opposite reaction: the brain receives a signal of temperature drop, and the vessels constrict sharply.

Specialists warn: a sharp temperature drop can become negative stress for the cardiovascular system. The first seconds of immersion are especially dangerous, when the body experiences maximum shock.

Recommendations for Safe Leisure

In conclusion, hydrometeorologists urge citizens to remember safety. Swimming in the heat is not only a way to cool down and improve blood circulation but also a potential health risk. To minimize stress on the body, it is recommended to:

  • Avoid plunging suddenly into the water after prolonged exposure to the sun.
  • Gradually get used to the water temperature to give blood vessels time to adapt.
  • Monitor your well-being, especially for people with chronic cardiovascular diseases.

"We wish you a pleasant and safe holiday on the coast," they concluded at the Hydrometeorological Center of the Black and Azov Seas.