The building of the Haringvliet dam was completed in 1971, 14 years after the start. It bridged the 4.5 kilometres of water between Goeree-Overflakkee and Voorne Putte. Excluding the Oosterschelde barrier, the Haringvliet dam took the longest time to build. The Haringvliet dam had two functions. Firstly, it had to protect against a potential flood. Secondly, it had to take care of the drainage of water from the Rhine and the Maas into the North Sea. Consequently, the dam had to be an open dam. Seventeen openings regulate the amount of water which flows through the New Waterway to the North Sea.
When the water levels near Rotterdam are getting too high, the special drainage sluices can drain off an increased amount of water into the sea. In addition to the drainage sluices, a lock was built for ships. A cable way was one method, amongst others, used to fill in the gap. To preserve wildlife, a number of piers were constructed within special tunnels. Fish can use these tunnels to swim directly from the Haringvliet to the North Sea (or vice versa), even when all locks are closed.