E.M.I.L.Y.

E.M.I.L.Y. (sometimes, EMILY or Emily; acronym for Emergency Integrated Lifesaving Lanyard) is a robotic device used by lifeguards for rescuing swimmers. It operates on battery power and is operated by remote control after being dropped into the water from shore, a boat or pier, or helicopter. Using an impeller motor to travel through water, it is able to reach victims much faster than a human lifeguard can by swimming, and it is more compact and less expensive to maintain than manned watercraft. It can also operate in weather and surf conditions that make other rescue attempts impractical. Once it reaches the victims its foam core allows it to function as a flotation device for up to 4-6 people holding onto side ropes or handles. 
Emily was created by inventor Anthony Mulligan and Robert Lautrup, and named after Marie Mulligan's friend, who died in a car accident. It was first tested in Zuma Beach near Malibu, California, and at Depoe Bay, Oregon and Westerly, Rhode Island beginning early 2010. In July 2012, lifeguards there made one of the first rescues using Emily, pulling a father and son to shore after they had been caught in a rip current.
A new multi-day duration gasoline powered variant of EMILY for ocean-based storm tracking and weather data collection has been developed under funding by NOAA.
In January 2016 EMILY joined a Roboticists Without Borders team from The University of Texas A&M Center for Robotic Assisted Search and Rescue on a successful mission to Lesvos Island, Greece to assist in ocean rescues of Syrian refugees crossing the Aegean Sea from Turkey to Greece. In the first few days of embedded missions with the Hellenic Red Cross, EMILY assisted the Red Cross and other lifeguard organizations to help 250+ refugees safely come ashore on Lesvos. There are currently systems with the Hellenic Red Cross, the Hellenic Coast Guard, and in Turkey.
References.
https://www.npr.org/sections/alltechconsidered/2016/03/22/471285293/how-a-high-tech-buoy-named-emily-could-save-migrants-off-greece
External links.
https://www.wired.com/2016/01/a-robot-life-preserver-goes-to-work-in-the-greek-refugee-crisis/