The swimmers were analyzed when passing through a parallelepiped calibrated space with mean dimensions of 4.82 m1.11 m1.85 m for the horizontal (main movement direction), vertical (pool depth) and lateral (lane width) directions, placed in contact with the turning wall and the water surface. Five stationary mini-DV video cameras (Sony DCR-HC62E and DCR-HC96E, 50 frames per second, shutter speed: 1/120 s) were located underwater at different depths in waterproof cases (Sony SPK-HCD) on a semi-ellipse centered on the turn place (Fig. 1). Their synchronization was obtained using an underwater strobe flash.