Drag is the term used to identify the resistance of water to swimmers' movements through it. That resistance is caused by a difference in pressure between the water in front of and behind swimmers. Objects tend to be pushed from areas of high pressure toward areas of low pressure. Consequently, if the pressure of the water in front of swimmers is greater than the pressure behind, their speed will be decreased unless they can overcome the added pressure by stroking with greater force. The reduction in speed will be in direct proportion to the magnitude of the difference in water pressure in front of and behind the body.
