This paper investigates the performance of the dual mode,namely flipper mode and central pattern generator (CPG) mode,for controlling the depth of a gliding robotic dolphin.Subsequent to considering the errors in dynamic models,we propose a depth control system that combines the line-of-sight (LOS) method with an adaptive control approach (ACA) to deal with uncertainties in the model parameters.First,we establish a full-state dynamic model to conduct simulations and optimize the parameters used in later aquatic experiments.Then,we use the LOS method to transform the control target from the depth to the pitch angle and employ the ACA to calculate the control signal.In particular,we optimize the ACA's control parameters using simulations based on our dynamic model.Finally,our simulated and experimental results demonstrate not only that we can successfully control the robotic dolphin's depth,but also that its performance was better than that of the CPG-based control,thus indicating that we can achieve three-dimensional motion by combining flipper-based and CPG-based control.The results of this study suggest valuable ideas for practical applications of gliding robotic dolphins.