Apparatus is provided for attaching a fin to the underside of a small watercraft, such as a surfboard. The apparatus includes a holder which is attachable to the underside of the surfboard, so that a recess defined in the holder extends inwardly from the underside. The apparatus further includes a fin sub-assembly comprising a fin and a body which is receivable within the recess defined in the holder. The fin sub-assembly can be received in the holder in a plurality of angular orientations about an axis generally perpendicular to the underside of the surfboard. The invention extends to a holder, a small watercraft, and a method for attaching a fin to an underside of a small watercraft.