Hiccups occur when swimming mainly for the following reasons: First, the inward pressure of water on the abdomen in the water can cause the organs to be squeezed, the stomach is a cavernous organ, and when subjected to the pressure of water, the gas in the stomach will be squeezed out and hiccups will occur. Secondly, the water temperature in a swimming pool is lower than the body temperature, which may cause the abdomen to get cold and the stomach to slow down, so the gas produced in the stomach cannot run down with the peristaltic movement of the stomach body, resulting in hiccups. Finally, the breathing movement during swimming is different from usual, and diaphragm spasm may occur during exhalation and inhalation, which may lead to hiccups. All of these conditions may lead to hiccups while swimming, so you should immediately adjust your breathing and avoid inhaling too much air through your mouth at the pool.