Swimming is a physical activity performed in an environment where human beings are not adapted from an evolutionary point of view. For this reason, swimming for humans is considered an ontogenetic movement and not a phylogenetic one such as walking or running on land. Locomotion into the water has some very specific characteristics for the human being, since the body experiences a situation of hydrostatic microgravity which in most cases enables flotation. Flotation capacity is affected by the physicochemical properties of the water (temperature and osmolarity) and by the body characteristics of the immersed person. In this situation: (1) joints no longer experience the load implied by supporting body weight on land, (2) blood flows more easily, and (3) the type of muscular work is basically concentric. Body balance is other important aspects to take into account, especially in swimmers with amputated limbs or limbs paralysis. Finally, the thermoregulatory response of the human body to changes in water temperature is also considered a useful and extended recovery method.