They're even better than the actual expendable sonar systems, because they're not constrained by battery life: the drone's rotors are covered in solar cells and can generate power after a little time under the sun. In addition, it can hunt for subs in flocks in case the Navy wants to scour a big area more quickly. Jones told the publication that as a sonobuoy replacement, the drone "[will] be on the water 23 hours a day, and flying maybe one hour a day." It was designed as a "launch and forget" system with a water-tight enclosure, though, so we're guessing it's tough enough to endure the ocean's harsh conditions. Speaking of drones that can take off from water, researchers from the Johns Hopkins University Applied Physics Laboratory created a similar machine called CRACUNS.