Abstract: A method of operation of marine locks includes the steps of supporting a first column of water within a lock chamber upon a vertically movable first floor, supporting a second column of water within a balance chamber upon a vertically movable second floor, supporting the first and second floors upon a confined volume of compressed air communicated between the lock chamber and the balance chamber and causing the first floor to rise or fall by application of upward or downward hydraulic pressure on the first floor while causing the second floor to move in the opposite direction by application of contrary hydraulic pressure on the second floor. Lock systems to perform the new methods are disclosed.