Seems to me this needs a section on canal/waterway tunnels (as opposed to water supply tunnels), e.g. Rove Tunnel, southern section of the Marseilles-Rhône Canal, 4.5 mi (7.2 km) long and 72 ft (22 m) wide, Bouches-du-Rhône dept., SE France; opened 1927. Starting near the village of Le Rove, it cuts through the Chaîne de l'Estaque at sea level. It is considered one of the greatest pieces of engineering since the Panama Canal. Longest canal tunnel in the world.