Controllable pitch propellers are actually already outfitted on something like ~30% of shipping vessels. https://www.savree.com/en/encyclopedia/controllable-pi

Controllable pitch propellers are actually already outfitted on something like ~30% of shipping vessels. https://www.savree.com/en/encyclopedia/controllable-pitch-propeller-cpp https://www.savree.com/en/encyclopedia/controllable-pitch-pr... But these use actuators to mechancially adjust the pitch rather than relying on deformation. Twisting a few props about a their axes is a lot simpler than the geometry changes that are required acros the control surfaces of a toroidal prop, however. I don't think that would even be feasible