Southern African Shipyards, the shipyard contracted to repair the Africa Mercy, has also been busy building new tugboats for the SA Port Authority. These tugs have an amazing propeller and rudder mechanism - known as a Voith Schneider Propeller - that uses blades underneath the hull to manouver the vessel. To see how the Voith Schneider Propeller system works click here. 
One of the new tugs is ready to be launched just alongside the Africa Mercy.
A close-up of the Voith Schneider Propeller.