: In this paper, we show the simulation result to find the suitable fish swimming modes(specially BCF swimming) for fishlike underwater robot system. To find the suitable swimming modes, we assume that they have the same length, volume, and weight, but the different numbers of actuator(joint). And we use the minimum number of the joint for each swimming mode. We derive the dynamic equation for each system using Kane’s method and these results are compared by DADS. We present the optimal solution of swimming mode for some aquatic locomotion, especially faster(high propulsive efficiency) and more maneuverable(quick turning motion). Copyright c 2005 IFAC