In a natural setting, many fish species will regularly turn, accelerate, and perform other unsteady behaviors, while occasionally swimming steadily in one direction. Even though such irregular maneuvers make up the majority of underwater life, we know little about them because it is difficult to repeatedly reproduce such behaviors in a laboratory setting. Here we ask how specific fins move to contribute to turning in fishes using a novel device to repeatedly elicit specific unsteady maneuvers. We have developed a programmable “car” with an attached flow-through chamber mounted within the working section of a flow tank. The car can move backwards and forwards in a controlled manner, which causes the fish to turn around, back up, or slow down. By manipulating the speed of the car as well as the speed of the flow in the flow tank, we are able to consistently produce many different unsteady behaviors, allowing an in-depth look into behaviors that are otherwise not very repeatable. Our method is robust and elicits repeated actions that are consistent among trials within one individual, between trials of different individuals of the same species, and even between trials of different species. We quantify fin movements including tail flaring, pectoral fin movement, and movement of the dorsal and anal fins in both bluegill sunfish and largemouth bass, using a computer vision technique called DeepLabCut. Our work is one step along the path to better understanding unsteady maneuvers in fishes and will improve our knowledge regarding the mechanics, morphology, and control systems behind behaviors that have previously proved difficult to observe in a consistent and controlled manner.