A fluid control device is provided for controlling and/or halting an uncontrolled flow of petroleum or natural gas from an open well head on the sea floor. The fluid control device includes an elongated member having a diameter smaller than the inside diameter of the well head casing. A tapered section in connection with the elongated section, has a diameter equal to or greater than the inside diameter of the well head casing. An end section connected to the tapered section has a diameter greater than or equal to the outside diameter of the well head casing. The fluid control device, under its own mass or under an external force, overcomes the upward forces created by the flowing petroleum or natural gas, resulting in sufficient downward movement of the fluid control device and contact with the open well to seal the well head casing or drill pipe.