A releasably submergible float assembly for use with a mooring line. The float assembly includes a buoyant float body and a retainer. The mooring line is passed through conduits in each of the float body and the retainer, and the assembly submerged to a depth by pressing down on the float body. When the downward pressing is released, the retainer prevents the buoyant float body from rising to the surface. The engagement of the retainer with the mooring line is actuated by the buoyant float body pressing against the retainer. Pressing down on the float body releases the engagement of the retainer with the mooring line, which releases the float assembly from its submerged position on the mooring line. The float assembly may thereby easily be relocated to a position on the mooring line when used in a longline culture system employing the “double backbone” configuration.
