The Thick Enemy

Water is 800 times denser than air. For swimmers, this defines everything. At elite speeds, the vast majority of a swimmer's energy goes to overcoming drag rather than moving the body forward.

Two types of drag dominate. Friction drag comes from water sliding along skin and suit surfaces. Form drag comes from pushing water out of the way, and it depends on the swimmer's frontal cross-section. A streamlined body position cuts form drag sharply, which is why coaches obsess over head position, hip height, and a tight kick. Even a slightly dropped chin enlarges the frontal area enough to cost a race.