Water-buoyant structure

A water-buoyant structure formed from concrete, the structure comprising an outer wall that surrounds a perimeter of the structure and an inner wall that surrounds the perimeter of the structure and is separated from the outer wall by a cavity, such that the cavity extends for the entire perimeter of the structure, the structure further comprising a base, wherein the outer wall extends to define an outer base wall of the base and the inner wall extends to define an inner base wall of the base separated from the outer base wall by the cavity, such that the cavity also extends for the entire base of the structure,

• wherein a plurality of longitudinal webs extend along and between the outer base wall and the inner base wall, to connect the outer base wall and the inner base wall and thereby divide the cavity that extends for the entire base of the structure into a plurality of elongate compartments, one or more of the plurality of compartments configured to be fluid-tight and able to be flooded with water and, optionally, emptied of that water, the elongate compartments further configured to allow controlled fluid communication between adjacent compartments.