An improved fin system for surfboards and other watercraft that utilizes a series of wide, flanged, fin boxes as a means of securing the fins into the base of the surfboard body. The fin boxes create a cantilever effect that provides additional strength and rigidity to the fins when compared to other available systems. Additionally, each fin tab of a fin can be installed into a self-contained fin box, thereby allowing for separation of the fin boxes once installed. The separation between the fin boxes permits increased longitudinal and torsional flex of the watercraft body when compared to a unitary fin box design.