See also: A life afloat for every budget
Built in 1926, the boat, called Xylonite, is featured in the Christopher Nolan movie with soldiers wading through the water to climb aboard.
And although it wasn't involved in the original evacuation, it was picked by the producers as a location because the interior and exterior are still perfectly in period.
Originally a sailing ship, it now has a motor, and is certified for sailing on the open sea. To take part in the filming, in fact, the 86-foot-long boat had to make it across the Channel - but is more usually to be found on a residential mooring at Limehouse Basin in East London.
Over the years, Xylonite has worked carrying cargo and giving boat rides to underprivileged children, but was sold to its present owners in 2011.
Since then, it's been thoroughly restored to create a four-bedroom home with nearly 1,400 square feet of living space. There's a whopping 28-foot living/dining room, with a wooden floor and panelling, and a fitted kitchen that's big enough for a range cooker and plenty of storage space.
The mooring costs around £875 a month, and while the owner will have to pay council tax, there won't be any stamp duty on the purchase.
Operation Dynamo involved the evacuation of 330,000 Allied soldiers from the beaches of Dunkirk in 1940 by a flotilla of yachts, pleasure boats and tugs - including 16 Thames sailing barges like Xylonite.
Dunkirk, starring Tom Hardy, Mark Rylance and singer Harry Styles, was released last month. And the owner of Xylonite even got to appear in the film as an extra, along with several of his friends.