A group of children, mostly wearing swimsuits, lie on their stomachs on a concrete surface

A group of children, mostly wearing swimsuits, lie on their stomachs on a concrete surface. A man in a light green shirt and black shorts stands behind them. They are near a swimming pool and a fence made of thin wooden poles. The children appear to be doing some kind of exercise, possibly related to swimming instruction. They lift their upper bodies while keeping their legs flat on the ground, in a back-extension type of exercise. The environment is bright and appears to be outdoors.