It's Driven by Egg whisks!

As you can see under the stern of the Sea Challenger. there are no propellers, just these strange vertical rotating vanes in three groups, which are able to hold the ship precisely in position when planting the wind turbines precisely on the sea bed.
But they move the ship pretty nicely too.
At the stern you can see two of the rotating turbine housings that will carry the wings that are rotated by the wind