Zhang Shengwu demonstrates how to operate his self-made submarine on April 27, 2016. Zhang, from east China's Anhui Province, invented the submarine in two months, at a cost of only 5,000 yuan (about USD$770). He obtained a patent for the invention granted by the State Intellectual Property Bureau. The submarine, measuring 6 meters in length and 1.2-1.5 meters in width, weighs 2 tons, with a 3-ton displacement. The submarine can dive more than 1 meter underwater, and boasts a driving speed of 7 nautical miles per hour. [Photo: gmw.cn]