The Shenzhen-Zhongshan Bridge's first and widest section of undersea tunnel was undocked successfully on Saturday in south China's Guangdong Province. The immersed tube will be put into the seabed for the construction of a tunnel in 2021, which is part of the Shenzhen-Zhongshan Bridge. It took 150 minutes to undock the tube by seizing the high tide and strictly following the undocking procedures.