A 10-year-old girl in Bangor, Wales, was saved from drowning when she blacked out in a swimming pool, after a set of computer-linked underwater cameras alerted lifeguards. The Poseidon system, currently installed in eight U.K. pools, and over two dozen in the U.S., uses a series of overhead and underwater cameras to track movement in a pool. When a swimmer disappears beneath the surface, software triggers an alert, which can help a lifeguard reach the victim more quickly. In this case, the computer issued an alert within 10 seconds after the girl, who was swimming in the deep end of a 12-foot deep pool, sank to the bottom. Of course, the system is no substitute for lifeguards — or for parents keeping an eye on their kids.