Abstract: A pivotable fin system, for use with an aquafoil such as a surfboard, comprising a plug and a fin having a main portion and a tab. The plug mounts in the surfboard, and has a central slot for receiving the tab. The tab has a reverse taper that matches a reverse taper in the central slot. The tab has at least one vertical slot which compresses to allow the tab to be mounted in the central slot, the vertical slot expanding once the tab is fully inserted into the central slot, the tab then securely held in place by the matching reverse tapers of central slot and tab. The tab has at least one tab cut for allowing the main portion of the fin to pivot with respect to the tab, allowing the main portion of the fin to self-align to a position where it reduces drag and cavitation.