Harbor tugs are more commonly equipped with these: https://en.wikipedia.org/wiki/Voith_Schneider_Propeller https://en.wikipedia.org/wiki/Voith_Schneider_Propell

Harbor tugs are more commonly equipped with these: https://en.wikipedia.org/wiki/Voith_Schneider_Propeller https://en.wikipedia.org/wiki/Voith_Schneider_Propeller They're quite efficient (although maybe only for lower speeds) and provide extreme maneuverability.