An asymmetric boat anchor has an unballasted fluke (2), with a tip (6) and a back (8) with a curved edge (10); a shank (4) is mounted on the fluke. The edge (26) of the shank away from the tip (6) of the fluke is curved and the free end of the shank (18) is offset from a plane (30) tangent to the back edge (10) of the fluke and to the edge (26) of the shank. Thus, if the anchor is in a reverse position, contacting the sea ground through the edge of the shank and the back edge of the fluke, it will roll on the edge of the shank and turns to the anchoring position.