A farmer in southeast China who designed and built a submarine has received a patent from the State Intellectual Property Office, mainland media reports. Zhang Shengwu, who lives in Maanshan in Anhui province, said he came up with the idea while watching a TV show, according to QQ.com. He started the project while his wife was away visiting her mother, and he worked on it every night for the next two months, joining together 5mm-thick steel plates. The final product measures 6 metres long and 60cm wide, offering just enough room for one person, according to the report. It can “dive” to a depth of one metre, but Zhang won’t be hunting down maritime threats in Maanshan any time soon. The design doesn’t allow for an air supply, so he must rely on a pipe that runs to the surface to provide oxygen. Its top cruising speed is 7 nautical miles per hour. His contraption was impressive enough to receive a patent certificate from the State Intellectual Property Office in February.