Swimmers on scholarship at the Australian Institute of Sport are periodically filmed to analyse their stroke technique. This is done from an underwater viewing room, using a Photosonics High Speed Camera, set at a filming speed of 100 frames a second. Two separate views of each swimmer are filmed in each of his/her competitive swimming styles. The first view is obtained as the swimmer passes at race pace across the front of the camera, three lanes distant from the window. The camera is panned during filming to obtain a maximum image size of at least four arm strokes. The second view of each swimming style is obtained as the swimmer moves at race pace directly toward the camera from the other side of the pool. Here, the camera is zoomed out as the swimmer approaches the window to maintain optimum body size for at least four arm strokes. By using a split image on the film and a reverse periscope on the camera, both above and below water level images are obtained on each film frame. Each stroke is analysed qualitatively by screening the film through a projection analyser at a projection speed from still frame to 24 frames per second. Reviewing the film at 24 frames a second slows the action to four times slower than actual performance speed. Slow motion is required to identify the movement patterns of the limbs, as activity viewed at normal performance speed occurs too quickly to identify problems in the swimmer's style. Some problems in stroke technique which have become evident in more than one swimmer, through this analysing process, are listed in this publication.