A floating plant (8) comprises a container (1) and a mooring element (2) provided with respective guide elements (10, 13). The guide elements have a mutual complementary shape such that the container (1) and the mooring element (2) may move freely with respect to each other in directions that coincide with the container central axis (CL). A plurality of elongated buoyancy elements (10) are arranged on the container outside and arranged between the container bottom end (17) and the container upper end (18), preferably parallel with the container central axis (CL). The container may be transported to the installation site, floating in the water and stabilized by means of the buoyancy elements (10). The mooring element (2) may be transported to the installation site, either in one piece or on several pieces (2a, 2b), and mounted such that it surrounds a portion of the container. The container is raised and lowered in the body of water by controlling the amount of water in the container.