Abstract: An aquatic ski for human propulsion generated by deambulatory action having a floatable hull and a propulsive oscillating fin assembly. The fin assembly includes a foot seat pivotally connected to the hull and a movable fin in articulated and cooperative connection with the foot seat. The movable fin has a plurality of free oscillating vanes pivotally connected between a pair of parallel arms. The oscillating vanes are movable between a position aligned with the arms and a position transverse to the arms. The hull has a forward portion and a rearward portion pivotally connecting together. The hull includes flotation chambers forward and rearward of the foot seat.