A liquid storage and delivery system, comprising: a rigid outer container (110; 310); at least one inner container (120; 320) disposed within the outer container (110; 310), the at least one inner container (120; 320) being expandable and collapsible and in fluid communication with a controlled opening provided with an isolation valve; characterised in that it comprises a balance assembly disposed on the outside of the outer container (110; 310), fluidly connected to a space between the at least one inner container (120; 320) and the outer container (110; 310) and configured to pressure balance the containers (110, 120; 310, 320) as the system is lowered to a sea floor, as the at least one inner container (120; 320) is emptied, and as the system is recovered from the sea floor, wherein the balance assembly comprises: one or more isolation valves; one or more check valves; wherein the one or more isolation valves are configured, when closed, to isolate the space between the at least one inner container and the outer container and the balance assembly from seawater flow, and wherein the one or more check valves are configured, when open, and when the one or more isolation valves are open, to allow seawater flow through the balance assembly to the space between the at least one inner container and the outer container, at least one flexible bladder intermediate the outer container and the one or more isolation and check valves (136, 137), fluidly connected to the space between the at least one inner container and the outer container, wherein the at least one flexible bladder provides for the containment of internal fluid during recovery operations of the system. a rigid outer container (110; 310); at least one inner container (120; 320) disposed within the outer container (110; 310), the at least one inner container (120; 320) being expandable and collapsible and in fluid communication with a controlled opening provided with an isolation valve; characterised in that it comprises a balance assembly disposed on the outside of the outer container (110; 310), fluidly connected to a space between the at least one inner container (120; 320) and the outer container (110; 310) and configured to pressure balance the containers (110, 120; 310, 320) as the system is lowered to a sea floor, as the at least one inner container (120; 320) is emptied, and as the system is recovered from the sea floor, wherein the balance assembly comprises: one or more isolation valves; one or more check valves; wherein the one or more isolation valves are configured, when closed, to isolate the space between the at least one inner container and the outer container and the balance assembly from seawater flow, and wherein the one or more check valves are configured, when open, and when the one or more isolation valves are open, to allow seawater flow through the balance assembly to the space between the at least one inner container and the outer container, at least one flexible bladder intermediate the outer container and the one or more isolation and check valves (136, 137), fluidly connected to the space between the at least one inner container and the outer container, wherein the at least one flexible bladder provides for the containment of internal fluid during recovery operations of the system. one or more isolation valves; one or more check valves; wherein the one or more isolation valves are configured, when closed, to isolate the space between the at least one inner container and the outer container and the balance assembly from seawater flow, and wherein the one or more check valves are configured, when open, and when the one or more isolation valves are open, to allow seawater flow through the balance assembly to the space between the at least one inner container and the outer container, at least one flexible bladder intermediate the outer container and the one or more isolation and check valves (136, 137), fluidly connected to the space between the at least one inner container and the outer container, wherein the at least one flexible bladder provides for the containment of internal fluid during recovery operations of the system.