Abstract: A disc-shaped marine structure fabricated of steel and/or concrete, able to support useful loads as great as 125,000 tonnes, is tethered to float stably in very deep water, with only minor response motions to wave of large amplitude and long period. A planar base disc of diameter about 135 up to 200 meters carries a centered primary buoyancy tank of span 2.5 to 4.5 times the draft. The strongly braced sidewall of the tank is spaced about 10 meters inward of the disc edge, defining one wall of an upwardly open confinement chamber. A thin cylindric outer shell wall extending upwardly from the margin of the base has about 26% to 35% of its area comprised of tubular passages set radially, of length and diameter about one meter or more. Radial bracking frameworks of 50% aperturing interconnect the tank with the base disc and outer wall.A mass of seawater approximately equal to the structure's displacement is largely confined, its volume/aperture ratio being about 800 m.sup.3 /m.sup.2.

Abstract: A breakwater comprised of an array of aligned perforated-wall caissons having a slab bottom standing on a pervious rubble base and anchored by its own weight incorporates exceptionally heavy ballasting to ensure stability under attack by large waves, i.e. to that the ratio of maximum horizontal thrust force to downward vertical force is below about 0.46.The immersed wall height is much reduced so that the slab bottom lies below mean sea level about 1.3 to 1.7 times the height of the greatest wave predicted, lessening costs of construction and siting. Efficient energy dissipation function is preserved by placement of augmenting mass below the height of the wave trough and by providing flow passages for jets directed by front wall ducts, avoiding increase of reflection coefficient.

Abstract: A ballasting block for use as chamber floor loading in a concrete caisson breakwater made up of horizontally-arrayed sections having perforated front walls, or for use as armor capping on rubble mound breakwaters, is of parallelepipedic form with two pairs of sides meeting at right angles, and front and rear end faces of rectilinear outline having openings recessed therein defined by at least one through passage extending the length of the block, serving as flow-guiding channel means. A preferred form for caisson ballasting as one or more layers of closely-spaced blocks, is a cube, or a rectangular prism, molded of concrete of weight from about one tonne to about twenty tonnes, having a single passage of circular, elliptical, or polygonal cross-sectional outline with area from 0.2 m.sup.2 to 1.5 m.sup.2. When used for armor capping each end face is perforated by a number of ducts, the blocks being laid in ordered arrays with close spacing presenting one end face upwardly.