Mystery of huge abandoned concrete block known as 'The Cement Ship' sitting on eerie sandbar off coast is finally solved

One of Washington state's most enigmatic landmarks has been identified as the result of a short-lived experiment in ships made of concrete more than a century ago.

The 'cement ship' lying abandoned on a sandbar outside of DuPont has puzzled visitors to the area since the 1960s.

Split into two pieces after decades of battering from the waters of Nisqually Reach, the massive hulk still attracts curious sightseers who can walk to it at low tide.

But the 100 foot ship was launched as part of a bold attempt to build ocean-going concrete 'tank boats' to transport fresh water along the coast of the US in the years after the First World War.

'The over-arching conditions at the time, those that led to the US concrete ship construction program was a scarcity of vessels during wartime, combined with a shortage of steel,' wrote bloggers Richard Lewis and Erlend Bonderud.

'We are under no illusions that we are extremely, compulsively and rather eccentrically, obsessed with this subject matter.'

The boat was named Captain Barker and was one of five built by the Great Northern Concrete Shipbuilding Company in the spring of 1919.

They costed $80,000 each - $1.4 million in today's money, and were designed to carry 52,000 gallons of fresh water each.

They could be built quickly but their heavy construction made them sit low in the water and just two of them survived more than a year with the rest sinking in storms.

'Seafaring men in Portland took an 'I told you so' smile today when they heard of the disasters which overtook the army tug Slocum and her escort of concrete barges off the Oregon shore,' the News-Pilot reported in January 1920.

The stone boats were not properly constructed for sea trips, and the trip down the coast should never have been undertaken, commented sea captains'.

Experimental boats made of concrete were first built in 1848 and the British navy built and launched 64 immediately after the First World War.

The US built 104 during the Second World War as it struggled to get naval production up to speed after the attack on Pearl Harbor, seven of which remain afloat today.

The 491-ton Captain Barker launched on March 3, 1919 but was quickly docked for repairs after its first sea trials revealed steering problems.

The fleet was also dogged by the lack of internal baffles which allowed sea water to slosh about the already unstable boats.

The Captain Barker was tugged by the Slocum from Vancouver to Astoria in January 1920 with a Captain Enos Crawford in charge.

It was put up for sale that October when its manufacturer filed for bankruptcy.

And it was more than 18 months before it found a buyer from the Rouse Towboat Company which renamed it Foss 103 and used as a sludge-disposal barge.

Its inglorious career came to an end in the 1960s when it was scuttled on the shore of Nisqually Reach where it lies to this day.

Its one surviving sister ship, the Captain Bootes, had been scuttled in the 1950s outside Everett.

But the wrecks of both boats have now spent half a century serving as valuable breakwaters, protecting their respective shorelines from tidal erosion, according to Chris Staudinger, the co-founder of Pretty Gritty Tours.

'This was especially favorable for the action because of it being concrete,' he told the News Tribune.

'They knew it was going to stick around for longer.'

'Whilst on our concrete ship research journey, we became acutely aware that the internet is literally littered with Urban Myths, half truths, fantasy and fiction about concrete ships,' wrote Lewis and Bonderud on their blog thecretefleet.com.

'We are always looking for the slightest clue as to where a concrete vessel, that we know was built, is today. We have found literally hundreds of them.'