cofferdam
/ˈkɔfərˌdæm/
noun
- A temporary watertight enclosure built in a body of water to allow construction or repair work to be done in a dry area.
- The engineers used a steel cofferdam to keep the river out while they built the dam.
- Workers built a cofferdam around the bridge pier to repair the foundation.
- A cofferdam was constructed so that divers could work on the underwater pipeline.