This invention relates to containment booms and more particularly to a device particularly adapted for attaching a containment boom to any ferromagnetic surface at the water line, the device including a base member in the form of an elongated arm having a medial portion and opposite end portions, a float at the medial portion of the arm for imparting buoyancy to the device relative to a body of water, a magnet carried by a first of the opposite end portions for magnetically attaching the device to a ferromagnetic surface, a second of the opposite end portions including a loop for connecting a line thereto for applying a force to the device to detach or disconnect the magnetic connection thereof with an associated ferrometallic surface, and first and second couplers for respectively fixedly and movably connecting a containment boom to the device.