This paper describes numerical methodology to model and investigates the shock waves and bubble dynamics produced by an underwater explosion when it happens under limited waters.The nonlinear dynamics results were calculated by ANSYS-AUTODYN explicit software.CL-20 was studied as basic research object in underwater test.It was shown that pressure and impulse histories for simulation are in good correspondence with the data calculated by empirical formula.The results calculated by empirical formula and AUTODYN was compared in order to corroborate the accuracy of numerical results.