Able-bodied seamen, decorative sails meant to evoke fish fins and dozens of security cameras will eventually make up the on-board complement of a mysterious four-story barge being built by Internet company Google Inc.

The barge is actually a "technology exhibition space," that Google will move between several piers in the San Francisco Bay area and other West coast locations over the next two years, according to a 36-page information packet submitted in August to the Port of San Francisco.

"We believe this curious and visually stunning structure will be a welcome addition to the waterfront; an experience unlike any other that celebrates community, local organizations and the history of San Francisco," reads the document, which lists the project as being spearheaded by By and Large LLC.

The floating structure built of stacked shipping containers, and a twin vessel in Portland, Maine, have stirred intense speculation about their purpose ever since reports of their existence surfaced last month. Reports have theorized that the barges could be anything from floating water-cooled data centers to retail stores to luxury party venues.

Google has gone to great lengths to keep the details of the barges secret, requiring at least one U.S. Coast Guard employee to sign a non-disclosure agreement.

On Wednesday, Google finally acknowledged that it was involved in the barges, saying it was, "exploring using the barge as an interactive space where people can learn about new technology," but noting that plans could change.

Among the issues still to be ironed out are whether the structure will require permits from the San Francisco Bay Conservation and Development Commission.

The hulking steel structure, still under construction and currently moored on a pier in San Francisco's Treasure Island, is somewhat unsightly at the moment. But Google envisions it as an "unprecedented artistic structure" that will have a dash of "nautical whimsy," according to the information packet, which Reuters obtained through a request under the city's sunshine act.

The shipping containers will house a 13,276 square foot studio space, along with a rooftop deck and catwalks.

The vessel, which will be open from 10am to 10pm, will hold technology demonstrations on the second and third floors.

"The structure will stand out but at the same time will complement its surroundings with decorative sails that provide shade and shelter to the guests," the document states. "The sails are reminiscent of fish fins which will remind visitors that they are on a seaworthy vessel."

The barge will navigate the bay with the aid of tugboats, with plans to moor at San Francisco's Fort Mason, Pier 48 and Angle Island. A power generator and a 5,000 gallon diesel fuel tank will be stored on the pier.

A crew of 50 will tend to the vessel and studio, including a full-time Barge Master, "two able-bodied seamen and one ordinary seaman," as well as 37 "technology demonstration associates" and seven security guards.

More than 50 security cameras throughout the vessel will also provide "on-site monitoring."