Submersible bridge
[1] They lower the centre span to 8 metres below water level when they give way to ships crossing the channel.The submersible bridge's primary advantage over the similar lift bridge is that there is no structure above the shipping channel and thus no height limitation on ship traffic.However, the presence of the submerged bridge structure limits the draft of vessels in the waterway.The term submersible bridge is also sometimes applied to a non-movable bridge that is designed to withstand submersion and high currents when the water level rises.Media related to Submerging bridges at Wikimedia Commons