An immersed tube is a type of underwater construction method used primarily for building tunnels beneath bodies of water. This technique involves prefabricating large sections of the tunnel on land, then floating them to the construction site and sinking them into a pre-dredged trench on the seabed. Once in place, the sections are connected and sealed to create a continuous tunnel. This method is often used for projects like road or rail tunnels, as it minimizes disruption to the water surface and surrounding environment. Notable examples of immersed tube tunnels include the Holland Tunnel in the United States and the Seikan Tunnel in Japan.