Until the 1960s, Deep Cove was only accessible from the sea or via the Wilmot Pass walking track. In 1964, however, the cove saw the start of considerable activity as it became an important part of the Manapouri Hydroelectricity Project as the site of the tailrace tunnel from Lake Manapouri. A tunnel connects the cove with the lake. The tunnel was completed in late 1969, with the power station became operational the following year. A second tunnel was started in 1997 and became operational in 2002.