The computation of wave resistance with linear boundary conditions has been widely in use as a hydrodynamic design tool for more than two decades. Recently, in ship-wave resistance computations, the nonlinear free-surface boundary conditions are treated by means of various techniques. In the present study, the fully nonlinear free surface boundary condition is satisfied through an iterative procedure by an approximate representation of the deformed-free-surface geometry in a step-wise manner by quadrilateral panels. The effect of the above water geometry of ship can be taken into consideration in the present nonlinear approach. This is achieved by an adaptive panel generation technique presented in the study. Consequently, a computer code which employs the nonlinear free-surface condition is developed and its robustness is shown by bench-mark and validation studies. The versatility of the present nonlinear code as a design tool is demonstrated in a case study which aims to take the forebody above water geometry into account for reducing wave resistance.