The ship collision prevention reel can be used to detect when a ship comes into contact with the wire stretched on the boom of a container crane at a port. This wire reel is installed on the boom of a gantry crane (container crane), and the wire rope is stretched so that it surrounds the outside of the boom. When the boom of an operating crane comes too close to a structure such as the bridge of a moored ship, the wire rope is pushed, activating the limit switch within the wire reel. This brings the crane to an emergency stop, preventing a collision between the boom and the ship.