Their narrow hulls required them to be paddled in a fixed sitting position facing forwards, a less efficient form of propulsion than rowing with proper oars, facing backwards.
We've had fire-fighting drones, racing drones, heavy-lifting drones and even ambulance drones but never have we thought of attaching them to us as a form of propulsion.
A study involving a swimming robot has demonstrated that although this form of propulsion is not especially efficient, it provides very good acceleration - a desirable trait in an ambush predator.