SS (RMS) Douglas (III) – the third vessel in the line's history to bear the name – was a packet steamer which entered service with the London and South Western Railway in 1889 under the name Dora until she was purchased by the Isle of Man Steam Packet Company in 1901 for £13,500.

Douglas was a steel built, single-screw vessel constructed by Robert Napier & Co. of Glasgow.

Until 1901 all its ships had been ordered and built for it, with the exception of the two eminently suitable vessels Prince of Wales and Queen Victoria which had been bought in after their owners had unsuccessfully tilted at the Manx trade.

The ship had been working the Southampton service to the Channel Islands and was thus very well suited to the Irish Sea trade.

In addition, there was a considerable quantity of regular cargo, ranging from furniture to foodstuffs and even motor cars.

As she proceeded down river towards the sea, she attempted to cross the bows of the Artemisia, a ship of 5,731 tons which was inward bound to Liverpool with a cargo of sugar from Java.

The collision was followed by a lengthy and expensive legal wrangle in which it revealed that the Artmisia was waiting her turn to enter the dock and was lying a thousand feet off the entrance with just sufficient seaway to stem the flood tide.