I just looked at this again, and noticed and discovered a couple of errors:

- she was the sixth PB3511, the fifth was DMS OSPREY
- both the fifth and sixth were built without the raised wheelhouse and without the artic-barge fitments
http://www.shipspotting.com/gallery/photo.php?lid=1234790
http://www.shipspotting.com/gallery/photo.php?lid=1723842
The two were consequently sometimes referred to as SB3511.

At some time after the 9/2013 trials, when the Van Oord contract materialised, she was quickly modified to be able to work with Van Oord's big sand barges, by addition of the "monkey island" and the retro-fitting of the artic-barge links.

Not an error as such. I think that the story goes like this:

She was ordered as a fifth PushBuster 3511 (intended to be DMS STARLING), but was changed during construction and launched 1/7/2009 with a non-standard lower wheelhouse but still with the special hull fitments for service as a articulated pusher - now sometimes referred to as a ShoalBuster 3511. The other four PB3511 were like this:
http://www.shipspotting.com/gallery/photo.php?lid=1095988

She was only completed in 1/2014 as KAIKOURA for an intended charter to Thong Yong 2000 Marine Pte Ltd, Singapore alongside Shoalbuster 3209s TAUPO and OTAGO. That fell through, but DMS chartered her to Van Oord for a contract at the new port of Bronka, near Kronshtadt and she was quickly modified to be able to work with Van Oord's big sand barges.
Seen on return from Russia
http://www.shipspotting.com/gallery/photo.php?lid=2142665

Now she's got it, I suppose no point in taking it off.

She is also suitable for pusher work, so the extra bit is for extra height to have a view over the pushed object. But why such a basic, after market looking cabin on a modern designed tug. didn't her designers realize that the extra height was needed?

Great shot! I also would like to know what the extra bit is for. ?Better all round vision?

Who stay there? duty AB or officer?

Great photo, great tug, stupid looking extra accomodation on top of her bridge.