When a 5-year-old girl went overboard from a Disney Cruise Line ship over the summer, a special alert system played a key role in her swift rescue.

Disney Cruise Line ships are equipped with overboard detection systems. After the child lost her balance on June 29 and fell backward through a porthole on Deck 4, her father jumped in after her, according to a Broward County Sheriff’s Office report. Neither were named by police.

She fell about 49 feet to the water at 11:29 a.m., per the report, and the overboard alarm was activated at 11:30. By 11:31, an overboard alert was broadcast on the ship’s communication system, and the U.S. Coast Guard was notified. A rescue boat retrieved the father and daughter from the water at 11:49.

However, despite their apparent utility in those emergency situations, they haven’t been as commonplace as travelers might expect. Here’s what to know.

The technology can notify crew members of overboard incidents and help reduce response times. One such system called MOBtronic “uses a multi-sensor fusion approach combining best-in-class thermal cameras and radar technology,” according to Frederik Giepmans, Managing Director of MARSS Maritime.