A swim fin has at least one fastening member dimensioned to fasten the swim fin onto a user's lower leg between the user's knee and foot. A fin portion is connected to the at least one fastening member and extending laterally outwardly from the fastening member. The connection between the fin portion and the at least one fastening member permits the fin portion to be repositioned upwardly or downwardly relative to the user's lower leg along the at least one fastening member. The present swim fin is equally adaptable for use attached to a swimmer's forearm.