A water propulsion assembly operatively connected to a watercraft moving on or through a body of water, may produce a propulsive force by sweeping fins in an oscillating motion in a generally transverse direction relative to a longitudinal axis of the watercraft. The fins may be rotatable about a first axis coplanar to the center longitudinal axis of the watercraft. Drive members rotatable about a second axis that is canted relative to the first axis may be operatively connected to the fins. The oscillatory motion of the fins may be controlled by torque applied at the canted second axis by reciprocating the drive members in a plane generally parallel to the center longitudinal axis of the watercraft. The oscillating fins may provide a propulsive force during both oscillating directions of the fins as they sweep back and forth.