Abstract: A side fin (10) for a surfboard has a base edge portion (13) which in use juxtaposes the surfboard, a leading edge (14) and a trailing edge (15) which meet to define fin tip (16). Fin (10) has a substantially planar fin base portion (17) extending from base edge portion (13), and a substantially curved fin tip portion (18) extending from fin base portion (17) to fin tip (16). When the fin profile is viewed in the longitudinal direction of the surfboard i.e. from leading edge (14) to trailing edge (15), the profile of fin base portion (17) is substantially rectilinear and the profile of fin tip portion (18) is curved.