A retractable keel apparatus for a ship, in particular for a sailboat, including a lift device for a lowerable and retractable fin device having a fin (4) and a fin head plate (20) disposed thereon, the fin head plate making contact with a keel receptacle (5) provided for permanently attaching to a hull when the fin is lowered, the receptacle further having a locking device by which releasable locking can be produced between the fin head plate (20) and the keel receptacle (5). The invention should be designed such that, despite greater stability, including in the event of a crash, the device can be produced and integrated in ships as simply and cost-effectively as possible. For this purpose, the locking device has at least one, preferably a plurality of, preferably driven, longitudinally displaceable locking bolts (15) that can be displaced along a diagonally running displacement path.