In order to solve the "barren ground" problem occurring in the coastal areas of Japan and around the world and to revive the "forests of the sea", a research and application project employing restoration technologies for seaweed beds that use steel slag and humus materials is now underway. This paper gives a summary of this "sea forest" restoration project that focuses on the links between the ocean, rivers, and forests, and also reports on the progress made and discusses future developments.