Abstract: A fin assembly including a fin having a base portion, the base portion having at least one extension portion extending from the base portion, at least one extension portion mounting at least one engagement portion, at least one socket mount for substantially permanent inclusion in a watercraft to which the fin is to be mounted, the socket mounting having at least one opening corresponding with and complementary to the extension portion and engagement portion on the fin so that the at least one extension portion and engagement portion can be received in the respective openings; and a securing means for releasably securing the fin relative to the socket mount.