In this paper, using a novel event-triggered method, a robust $H_\infty$ depth tracking controller is designed for a remotely operated underwater vehicle (ROV). It is assumed that the desired trajectory of the ROV is determined by an operator outside of the vehicle based on its needed depth and obstacles in its path. It is also assumed that a wireless network is used to connect the user with the ROV. To decrease the communication rate between the controller and the ROV, a novel nonlinear event-triggered $H_\infty$ controller is designed. The effects of the disturbance on the system performance are also attenuated. Stability of the ROV under the designed event-triggered controller is proved through a theorem. Simulation results demonstrate that the error between the depth of the ROV and its time-varying desired trajectory converges to zero using the proposed event-triggered $H_\infty$ controller. It is also shown that the communication rate between the designed controller and the ROV is considerably reduced.
