A marine gate has a buoyant variable length barrier and a cable management system employing two cables or lines. An opening line extends through the barrier to move the barrier from an expanded position (gate is closed) to a retracted position (gate is open) via a winch. A closing line moves the barrier from the retracted position to the expanded position using a winch. A weight is attached to the closing line for moving a submerged portion of the line to the seafloor when the barrier gate is retracted and the closing line is payed out by operation of its winch. The weighted line allows a portion or the entire cable system to be under tension at all times. The resulting cable geometry allows vessel operators confidence in knowing the cable location in the water depths at the gate, whether the gate is fully or partially opened.