Yes, Mau Mau V is the sistership to Darnice III. Two things that are different in the designs are that Mau Mau V had a mast instead of an arch between the funnels and most remarkable, no helipad as Darnice III. Why it is remarkable? As far as I know, she was built for the Agusta family of helicopter fame... When she later became Blue Narwhal there was a helideck built and the stern was extended, including a massive gangway that could reach 180° around the stern. She also has got a big TV-dome over the bridge. Darnice has got an extended stern recently, so in fact both of them have now lost much of their initial beauty...
