This may result from going into the water too soon after eating, or when overheated, or from staying in so long as to become chilled. It is not serious for a swimmer who keeps his wits, but if he gets frightened it may cost his life. Turn on your back and keep your chest inflated. Float, and swim with the unaffected limbs. Even if you be far from shore, the cramped member may soon relax if you keep cool.