Abstract: A convertible bank anchor and mooring device with a locking cylinder is shown for use with watercraft. The anchor has an elongated tube, or pole, having a ball and socket coupling at one end joined to the side of the boat and an inverted, downturned hook member at the opposite end of the pole for engagement with a tree bough or trunk on shore. There is a lock and key cylinder associated with the socket of the coupling to prevent the unauthorized disengagement of the coupling when the bank anchor is reversed and used as a mooring device. The hook member has a longitudinal swivel connection to the pole, and the ball and socket coupling comprises a stationary socket mechanism attached to one sidewall of the boat having a housing supporting a fixed clamping jaw and a spring-biased clamping jaw urged toward the fixed jaw to provide a female socket.