Various methods are used to construct underwater tunnels, including an immersed tube and a submerged floating tunnel. The immersed tube method involves steel tube segments that are positioned in a trench in the sea floor and joined together. The trench is then covered and the water pumped from the tunnel.

Yes, underwater tunnels are a common feat of modern engineering and are generally constructed using one of two primary methods: immersed tubes or bored tunnels. Immersed tube tunnels are built by prefabricating massive concrete or steel sections on land, sealing them with temporary bulkheads, and floating them out to the site. They are then lowered into a prepared trench on the sea or river floor, linked together, and covered with a protective layer of rock. Examples of this include the Ted Williams Tunnel in Boston or the Hong Kong–Zhuhai–Macau Bridge tunnel. For deeper or more environmentally sensitive crossings, engineers use massive Tunnel Boring Machines (TBMs) to dig a path through the bedrock beneath the water's surface, as seen with the Channel Tunnel between England and France. These tunnels are engineered with sophisticated waterproofing, ventilation systems to manage vehicle exhaust, and emergency escape routes. While they are expensive to build, they provide vital transportation links without obstructing shipping lanes or being affected by surface weather conditions.