Apart from fin oscillation patterns, medial and paired fish fins help balance torques and generate thrust. These fins can undergo significant deformation during swimming, and are actively regulated for propulsion and maneuvering. Fish are capable of producing these morphological changes because they have independent intrinsic fin musculature. Concerning the vortex patterns produced by shark tails, the data suggests that they may be the result of active control of the shark tail by intrinsic musculature. The results from the skin denticle study indicate that the denticles improve swimming performance, reducing drag forces and possibly increasing thrust.