Not for the first, or the last time I am writing about a Maersk design, and on this occasion it is particularly unusual. Back in the 1970s in the North Sea, and probably everywhere in the world, semi-submersibles had a great deal of difficulty deballasting from operating to transit draught and the other way, and so it was necessary for the ships on the job to take all the cargo off the working deck into port prior to a rig move, then get out there and move the rig (we should remember that at that time virtually all the ships working on the UKCS were anchor-handlers). After the move they would go back to the base port pick up all the cargo, which was mostly drill pipe, and take it out again. As a result of this activity it seemed to some-one to be a good idea to develop a ship with an open deck forward on which the drill pipe, and containers could be stowed for the move and a clear, but shorter, afterdeck which would allow the efficient operation of the anchor handling activity. While it is not possible to be definitive as to whether this was the source of the design of the Maersk Ms it seems likely, although by the time they appeared in 1986 things had changed. By then most of the semi-submersibles out there had been modified with the addition of extra buoyancy to allow the transitions to take place without the deck load having to be removed. And in any case whoever had worked on the idea for Maersk had changed the open deck forward into a hatch. As an aside, the ships were fitted with a large central propeller and two smaller azimuthing thrusters aft. This was on the basis, one assumes, that it is still more efficient to conduct the power through a single large propeller rather than two smaller ones side by side. The two ships were provided with enormous winches, having two workdrums each capable of storing 3300 metres of 77 mm wire and two tow drums each capable of stowing 1900 metres of 77mm wire. These capacities and a 160 ton bollard pull made them desirable for the deeper water rig moves which were beginning to take place. The forward hatches were always something of a problem. Shell used the ships for a while, fitted with a TV camera based DP system, which allowed them to use the hatches, and in an early exploration project out in the Falkland Islands the ships were used to take cargo out there underdeck. At some point the Maersk Master was fitted with rail round the hatch, allowing containers to be stowed on top of it. The Maersk Mariner (Photo by Cesar Neves in 2009) was sent to the breakers in January 2015, and an interesting photograph of it being put ashore was posted on Instagram, with one comment from a viewer saying “If you ever worked on the Mariner you’d be glad to see it up the beach. In fact you’d probably want to grab a gas axe and get stuck in”. The Maersk Master was sold to a Nigerian company in 2013 and also made it the the Alang breaker’s beach in August 2015.