Abstract: A fish cage for cultivating fish comprises a hull shaped vessel composed of outer side platings, inner bottom platings, screen bulkheads and a deck. A device for floating a hull shaped vessel on the water is provided, and openings are formed in the outer side platings and inner bottom platings and covered with nets so as to let sea water flow in and out of the hull shaped vessel. The device for floating the vessel on the water is formed by tanks arranged on the upper side of the outer side platings to hold air. Openings are provided in the bulkheads and covered with nets affixed to the screen bulkheads for letting sea water flow in and out. Openings are also provided in the outer side platings on the bow and on the stern of the vessel for letting sea water flow in and out.

Abstract: The mobile marine drilling structure is of the submersible type for operation in ice-covered waters. The structure comprises a base for placing the structure on the sea bed, a hull extends from the base, and a deck is supported by the hull. The deck is located above the water line for conducting drilling operations. The hull has an internal frame assembly including ballast tanks, and external wall sections at different inclinations to the horizontal to engage and break up the moving ice masses encroaching on the hull. These external wall sections include a plurality of matching polygonal, frusto-pyramidal, apex-up and apex-down walls extending above the base, and two transitional wall sections to provide two inflection points to the hull.