Floating construction comprising: - a flotation base including at least one essentially hollow body, where the maximum horizontal dimension of the flotation base is greater than the maximum vertical dimension of the flotation base; - at least one shaft supported by said flotation base, and an equipment or installation intended to be supported on the shaft's head, wherein the floatation base, the shaft and the equipment or installation form a transport unit; - downward impelling means; and - at least three retaining cables, the corresponding upper ends thereof being attached to said flotation base, and the corresponding lower ends thereof being attached to said downward impelling means; wherein: - the floatation base is selectively fillable with ballast material and it is large enough to ensure stable self-buoyancy of the transport unit; and - in the operative condition of the floating construction, either said shaft is semi-emerged and said flotation base is submerged, or said shaft is emerged and said flotation base is semi-submerged; and characterised in that: - said downward impelling means comprise at least one massive element comprising at least one essentially hollow box, fully or partially filled with ballast material and means for regulating the volume and/or weight of the ballast material contained in said hollow box; - the downward impelling means and the retaining cables are arranged such that, when the hollow box is in ballasted condition, the massive element is suspended from said retaining cables and completely submerged, located below the flotation base and raised above the seabed, and the retaining cables are tensioned and exert on said flotation base a downward force that increases the stability of the floating construction; and - the massive element is self-buoyant when the hollow box is in an unballasted condition or in at least one partially ballasted condition. - a flotation base including at least one essentially hollow body, where the maximum horizontal dimension of the flotation base is greater than the maximum vertical dimension of the flotation base; - at least one shaft supported by said flotation base, and an equipment or installation intended to be supported on the shaft's head, wherein the floatation base, the shaft and the equipment or installation form a transport unit; - downward impelling means; and - at least three retaining cables, the corresponding upper ends thereof being attached to said flotation base, and the corresponding lower ends thereof being attached to said downward impelling means; - the floatation base is selectively fillable with ballast material and it is large enough to ensure stable self-buoyancy of the transport unit; and - in the operative condition of the floating construction, either said shaft is semi-emerged and said flotation base is submerged, or said shaft is emerged and said flotation base is semi-submerged; - said downward impelling means comprise at least one massive element comprising at least one essentially hollow box, fully or partially filled with ballast material and means for regulating the volume and/or weight of the ballast material contained in said hollow box; - the downward impelling means and the retaining cables are arranged such that, when the hollow box is in ballasted condition, the massive element is suspended from said retaining cables and completely submerged, located below the flotation base and raised above the seabed, and the retaining cables are tensioned and exert on said flotation base a downward force that increases the stability of the floating construction; and - the massive element is self-buoyant when the hollow box is in an unballasted condition or in at least one partially ballasted condition.