A hollow elongated cylinder has a cup with a central opening at one end and is open at the other. A plurality of equidistantly spaced like slots are cut into the cylinder wall and extend for a short distance in the axial direction from the other end toward the cap. An elongated bar parallel to the axis of the cylinder is secured to the inner wall of the cylinder, one end of the bar being adjacent the cap, the other end of the bar being adjacent the slots. A threaded bolt is aligned with the axis of the cylinder and is disposed therein, the head of the bolt being alignable with the slots, the end of the bolt extending through the opening of the cap. An eye is secured to the exposed end of the bolt. A flat circular disc has a central threaded bore threadedly engaged by said bolt, the disc being disposed in the cylinder and having a diameter slightly smaller than that of the interior of the cylinder. The disc has a portion cut away whereby the disc bears against the bar slidably but non-rotatably. A coil spring is disposed concentrically about the bolt inside the cylinder, one end of the spring bearing against the cap, the other end of the spring bearing against the disc. Each of a plurality of elongated arms extends through a corresponding slot, one end of each arm being disposed within the cylinder and engagable by said bolt head, a major portion of each arm extending outside of the cylinder. A like plurality of devices are disposed outside the cylinder, each device being aligned with a corresponding slot and pivotally securing each arm to said cylinder at a point intermediate its ends but adjacent the one end of the arm.

An anchor with collapsible flukes is provided with a spring tensioned latching mechanism which normally prevents the flukes from moving from a latched position to a collapsed position. The latching mechanism is unlatched and the flukes collapsed by a releasing mechanism including a compression spring and a firing pin. Tension on an anchor line draws the firing pin against the compression spring and, upon a sudden release of the tension in the anchor line, the firing pin is driven against the latching mechanism to unlatch it and permit collapse of the flukes.

A boat anchor which includes a hollow shank having a line attachment eye at one end and protruding fins at the other end. Anchor flukes are pivoted to the fins for movement between three positions, namely: an operative position extending generally laterally away from the shank, an anchor-releasing position in which the anchor flukes extend longitudinally of the shank and away from the line attachment eye, and a storage position in which the anchor flukes extend alongside the shank towards the eye; shear pins carried by the fins are broken by the anchor flukes under the application of a predetermined load to permit pivotal movement of the anchor flukes into their anchor-releasing position. A spring-loaded plunger resiliently maintains the anchor flukes in either one of their storage and operative positions. A stop bolt can be adjusted to block the plunger into a position in which it positively locks the flukes in their operative position, whereby anchor-releasing is no longer possible.