This is the moderately well known semi-submersible Ocean Guardian, now a bit antique, but so far avoiding the razor blade manufacturers. A few years ago it had a fairly successful adventure in Falkland islands waters. It is an Earl and Wright 700 Series which went to work in 1985. The oil industry liked these things because they are big, and you can get a lot of stuff onto their decks.

The photograph was taken by Alistair Morton as it was on its way up the Cromarty Firth being towed by one of the Gulf Offshore UT722s and the Bourbon Orca, back in 2012. 

 
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