The Herrenknecht Offshore Foundation Drilling is currently the largest offshore drilling rig and is being used by DEME, a global leader in dredging and land reclamation, solutions for the offshore energy market, environmental and infrastructure works, to install monopile foundations in Saint Nazaire. The first offshore wind farm in France is being built here. A total of 73 monopiles with a diameter of 7,700 mm have to be drilled at depths of between 6 and 24 metres. It is also the first offshore wind farm in the world where rock drilling for XL monopiles is one of the main installation techniques. The new offshore foundation drilling machine used for this purpose offers considerable ecological and economic advantages over conventional methods. At the same time, however, it poses a major challenge, as the huge machinery must be safely supplied with power from the ship. It was not only the corrosive environment that posed a problem for the safe cable routing. The long travel distances of the drill working deep in the rock also demanded a robust and reliable solution.