These giant jacks protect harbors from damaging current. As waves hit the tetrapods, the force of the water is dissipated by the curve of the legs. There are 1630 tetrapods on the ocean side of the Crescent City breakwater. There are 1900 tetrapods and 768 steel reinforced dolos on the newer leg of the jetty. This 25-ton tetrapod was on display near Front Street and was moved nearly three feet off a pedestal by the force of the March 28, 1964 tsunami.