Water exercise is particularly important for lifestyle disease prevention and long-term care prevention, and is prevalent among the middle-aged and elderly population. During water immersion, buoyancy acts on the immersed body and the influence of gravity is reduced. In addition, cardiovascular responses, caused by blood shifts from the abdomen and legs to the thoracic region, occur due to water pressure, unlike in the case of land exercise. Resting water immersion at thermoneutral conditions (about 34°C water temperature) induces an increase in stroke volume, a reduction in heart rate, an increase in cardiac output, and a reduction of total peripheral vascular resistance, unlike resting on land. During water exercise and the recovery phase of water exercise, there are similar cardiovascular responses due to changes in blood flow. The water temperature and water level cause changes in these basic responses. It has been confirmed that water exercise does not lead to excessive responses in blood pressure, and is effective in cardiovascular rehabilitation. In addition, water immersion during the recovery phase after exercise has attracted attention as a rehabilitative exercise modality. Previous studies have suggested that the effects of immersion on cardiovascular response in the rest, exercise, and recovery phases provide benefits to the immersed person, but further studies are needed to confirm the effective application of the methods.