Looks somewhat like this one,, also a kind of not fitting left or right

http://www.shipspotting.com/gallery/photo.php?lid=2658240

Interesting question where to categorise these?
Not a yacht, but a yacht's tender.
Does function to supply a yacht, but nothing to do with the offshore industry
"Workboats and tenders" seems the best we have, but still doesn't quite seem right.

I have raised this question on the Forum - please only reply there:
http://tinyurl.com/mbjgvdf

She's a supply ship. Due to visit the Pool of London tomorrow @ 15.45.

Looks like a tug! ;-)