What in tarnation is Google building on a barge in San Francisco Bay? The U.S. Coast Guard knows, after visiting the vessel on Wednesday, but it is not at liberty to reveal any more details thanks to a corporate gag order imposed on Coast Guard employees.

“We can confirm that Google is involved or associated with the barge but there is a nondisclosure agreement in effect; the Coast Guard is unable to discuss or divulge any further details at this time,” Coast Guard spokesman Petty Officer 1st Class Thomas McKenzie told CNBC.

The confirmation that the barge is in fact a Google creation is something, at least. The company has thus far refused to admit that it’s involved with the floating, four-story building that’s anchored off Treasure Island, in the middle of San Francisco Bay.

The San Francisco-based barge is one of four barges registered to a Delaware company called By and Large – the name of which some believe to be a dorky homage to “Buy N Large,” the fictional corporation from the movie Wall-E. The names of the barges also may be part of a nerd code. The vessels are dubbed BAL0001, BAL0010, BAL0011, and BAL0100. In binary – the 1s and 0s foundation of computing – these numbers represent “1,” “2,” “3,” and “4.”

Currently BAL0001 and BAL0010 are anchored in San Francisco (only BAL0010 houses the mysterious structure, however), while a second structure, built on BAL0011, was recently spotted on the other side of the country, off the coast of Portland, Maine.

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The San Francisco and Portland structures are similar, both constructed using empty shipping containers that have been welded together. Both have windows, meaning they are likely meant to have people inside them regularly. And both are fairly large. That, however, is where the knowns end, and the mystery begins.

As CNET first reported, the barge-buildings may be floating data centers that use sea water to cool Google’s servers. The company obtained a patent for floating data centers in 2009, and a person linked to both Google and By and Large referred CNET to the patent when questioned about the San Francisco barge.

According to CBS San Francisco, however, people familiar with the project say the S.F. barge will be used as a “floating marketing center,” or retail store, for Google’s much-hyped wearable tech, Google Glass. And the LA Times speculates (sarcastically) that it could be anything from a “doomsday flotilla” to a private paintball arena for Google executives.

The buildings are still under construction, so it will likely be some time before we find out what the heck Google is up to. In the mean time, we can only guess.

So, what do you think Google has planned?