https://www.forbes.com/sites/hisutton/2020/03/22/china-deployed-underwater-drones-in-indian-ocean/#83175aa66933

China has deployed a fleet of underwater drones in the Indian Ocean. According to Chinese government sources, the drones were launched in mid-December 2019 and recovered in February after making more than 3,400 observations. These Sea Wing gliders are a type of Uncrewed Underwater Vehicle (UUV) which can operate for months on end.