A fin box for releasable attachment of a fin having at least one fin-tab, the fin box adapted for insertion into and retention within a water board, the fin box including: a generally elongate body provided with a substantially rectangular recess open at a first surface of the body, the recess extending to a base proximal to a second surface opposite the first surface, and the recess having a forward end and a rearward end; wherein the structure is provided with at least one angled threaded hole extending from the first surface of the body to emerge at a point within the recess between the first surface and the base of the recess.