Abstract: A subsea unit suitable for storing hydrogen gas underwater comprises a weighting base and an array of interconnecting storage tanks on the base. The base may be cast from concrete on a deck of a vessel from which the unit is subsequently launched into water. A protective structure fixed to the base covers the array of tanks. A restraint system, comprising a series of strap restraints curving around the top of each tank, secures the tanks to the base against buoyant upthrust. The restraints are attached to elongate tensile members extending upwardly from the base, disposed on opposite sides of the underlying tank. The arrangement transfers loads efficiently from each tank to the base on load paths that bypass the other tanks.

Abstract: A subsea foundation for supporting a pipeline or a pipeline accessory has a mudmat and at least one pile arranged to anchor the mudmat by extending from the mudmat into seabed soil. A coupling that couples the pile to the mudmat has at least one interface member supported for angular displacement relative to the mudmat, such as a pivoting beam or a wedge-shaped adaptor ring, to accommodate the orientation of the mudmat relative to the pile.