An autonomous underwater vehicle (AUV) uses a model of propulsive efficiency to achieve high values of propulsive efficiency over a range of forward velocities, giving a lowered energy drain on the battery. Externally monitored information, such as that on flow velocity, is conveyed to an apparatus residing in the vehicle's control unit, which in turn signals the locomotive unit to adopt kinematics, such as fin frequency and amplitude, associated with optimal propulsion efficiency. In an embodiment, the model of propulsive efficiency is generated from a multilayer perception neural network model using data from aquatic species, such as undulatory fin propulsion in the knifefish (Xenomystus nigri), and a sensitivity analysis is used to lower the number of required inputs. Power savings could protract vehicle operational life and/or provide more power to other functions, such as communications.