Apparatus for use with fluid-processing plant configured to generate and store pressurized fluid. Fluid-processing plant is spaced apart from body of water. Apparatus includes variable-buoyancy assembly positioned in body of water in such way that buoyancy force urges variable-buoyancy assembly to move toward surface of body of water. Apparatus also includes non-collapsible fluid-line assembly positionally anchored, at least in part, underground in such way that non-collapsible fluid-line assembly extends, at least in part, into body of water. Non-collapsible fluid-line assembly fluidly connects fluid-processing plant and variable-buoyancy assembly together in such way that non-collapsible fluid-line assembly conveys pressurized fluid between fluid-processing plant and variable-buoyancy assembly. Non-collapsible fluid-line assembly transmits an anchoring force from ground to variable-buoyancy assembly; this is done in such way that anchoring force substantially counteracts, buoyancy force acting on non-collapsible fluid-line assembly. Anchoring force substantially urges variable-buoyancy assembly to remain below surface of body of water.