Sonar signal simulation is an important area of research for industrials and scientific of the domain. Indeed, it can be used in many ways by sonar manufacturers, both for designing a system or in order to explain physical phenomenon on data. Therefore, by minimizing the expensive testing time at sea, a well designed simulator can be a very interesting financial asset. Traditional sonar signal simulation also contains problems to be dealt with. It is often necessary to find a balance between the computational power consumption, the needed accuracy of the physical phenomenon description and the scale at which simulated signals are relevant. In our simulation model we propose a solution based on a very dense grid (resolution of about the concerned wavelength) of extended scatterers spread on the seafloor. It is designed to describe efficiently the backscattering strength and the phase response of the seafloor for every type of sonar.