In this paper, the validation of the mathematical model for an aquatic robot is presented, by implementing it in MATLAB´s Simulink toolbox to evaluate the system's natural behavior and then running it on a dSPACE card. Subsequently, a PID control for the robot's depth, which is programmed, compiled and runned on the Fox Board G20 embedded system, will be designed, in order to apply the "Hardware-in-the-loop" simulation methodology and test the Fox Board as the simulated plant's controller. For this, the dSPACE card is physically connected to the embebbed system through a RS232 communication protocol, where the data used for simulating the operation of sensors and actuators that make up the robot, are sent and received.