An underwater robot of a joint team of University of Melbourne and University of Sydney dives during the World Intelligence Underwater Robots Challenge held in north China's Tianjin, May 15, 2019. The World Intelligence Underwater Robots Challenge opened here on Wednesday, attracting 13 teams from China, the United States, Japan and Australia. The competition, with the theme "Dream pursuer in the water, intelligence winner in the future," is one of the five competitions being held during the third World Intelligence Congress. (Xinhua/Yue Yuewei)