Google's mysterious barge moored in San Francisco Bay will not become the glitzy showroom it is expected to be any time soon, as the search giant finds itself at the mercy of the US Coast Guard.

Google Barge
Work on Google's San Francisco barge delayed due to US Coast Guard investigation. (Reuters).

Design changes demanded by the Coast Guard must be made to the enormous barge's interior before it can be completed and opened to visitors, putting the project on a "hiatus" which could last until late spring.

Speaking to technology website Cnet, Brad McCrea, director of regulatory affairs for the San Francisco Bay Conservation and Development Commission, said: "A variety of senior BCDC staff members have met with Google's representatives to learn about its plans.

"We have learned that the barge is still under construction, albeit in a hiatus, and likely will not be completed until late spring 2014. In addition, Google is still exploring options for how to use the barge when it is completed."

McCrea added it is his understanding that "the design changes are to the interior of the vessel, as requested by the Coast Guard."

The website claims, during "numerous" recent visits to nearby Treasure Island, the barge has not had anyone onboard for some time, except for a single security guard.

Documents released under the US Freedom of Information Act in November provided some information about the barge, which is very similar to another Google-owned vessel moored off Portland, Maine.

The documents describe the San Francisco barge as 13,726 sq ft in size, with the ability to move between different locations. Once completed, the vessel is planned to feature sails resembling fish fins, but these will be decorative, as the barge is powered by diesel engines.

It was also revealed by the documents that each barge will be staffed by 50 people, including 37 "technology demonstration associates" - sales assistants in English.

Google anticipates up to 1,000 visitors per day according to the documents, but the barge can also be used to host private evening events running until after 10pm.

'A barge housing the last remaining dinosaur?'

The barge was at first thought to be a huge showroom to demonstrate Google Glass, which is expected to go on sale to the general public next year, and while the company has not denied this, it said jokingly in a recent statement:

"Google Barge...a floating data centre? A wild party boat? A barge housing the last remaining dinosaur? Sadly, none of the above. Although it's still early days and things may change, we're exploring using the barges as an interactive space where people can learn about new technology."

According to Reuters, Google has forced at least one US Coast Guard to sign a non-disclosure agreement, while another unidentified person, an inspector for a Californian government agency, admitted having to do the same.

San Francisco-based, CBS-owned television station KPIX 5 claims to have been told by multiple sources that the barges have been planned for over a year.

The sources said the barges were the brainchild of the search company's secret Google X skunkworks facility - also behind the development of Glass - and represented the company's attempt to upstage Apple's renowned retail stores.