While Google did not confirm the development, CNET reports it has evidence suggesting the 'secret project' could be a Google sea-faring data center.
Google patented a 'water-based data center' in 2009, describing an environmentally friendly, sea-powered telecommunications and storage system:
"A system includes a floating platform-mounted computer data center comprising a plurality of computing units, a sea-based electrical generator in electrical connection with the plurality of computing units, and one or more sea-water cooling units for providing cooling to the plurality of computing units"
While it is hard to say for sure that the structure is in fact a floating data center at the moment, Google, the technology giant, has a history of putting data centers in places with cheap cooling, as well as undertaking odd and unexpected projects like trying to bring Internet access to developing nations via balloons and blimps.