Abstract: A fin assembly for assisting a body or body board surfer in steering comprises a fin member of vane-like, generally planar shape and a securing device for securing the fin member to the limb of a surfer so that the fin projects generally downwardly into the water from the undersurface of the surfer's body. Preferably, oppositely directed right and left hand fin members are provided for securing to right and left hand limbs, respectively, of the surfer. The fin member has an enlarged base from which the fin projects, and the securing device is designed to secure the base against the appropriate limb so that the fin projects generally outwardly.