Here is the old Sedco Express built in 2000 in France - Sedco was a sort of French company - one of four very unusual semi-submersibles. When the built it they must have thought "why the hell do we keep putting the derrick in the middle when it would be must more convenient to have it on the end". There is a good reason as it turns out. The movement is minimised in the middle and maximised on the ends, which makes this class of unit limited to work in the more benign areas of the world. I think it may have gone, or be on its way to the breakers.

Photo taken by Gaetano Spiteri in January 2013 and posted here on 17th June 2019.