Two submersible bridges were constructed at either end of the Corinth Canal in Greece. To let ships pass through the canal, the bridges' decks are lowered 26 feet below the water level. This allows for ships of any height to pass through the canal, as there is no bridge structure above the canal to interfere with ships' masts, sails, or other parts of the ships. However, since the canal was constructed in the late 1800s, the canal is too narrow for some modern ships to pass through. Even with this constraint, approximately 11,000 ships go through the canal each year.
Sources:
Allen, David H. How Mechanics Shaped the Modern World. 2014.
By Original: Aspiasia Coumiotis Derivative work: Spilla at English Wikipedia (File:BridgeSubmerging.jpg) [CC BY-SA 2.5 (https://creativecommons.org/licenses/by-sa/2.5)], via Wikimedia Commons
