New York - A mystery underwater craft has been spotted close to the Verrazano-Narrows Bridge by New York Harbor ahead of Wednesday's lunar eclipse.
Observers say it may have been surveying the site of a shelved 1990s project to build a massive $40 billion tsunami shield on the Hudson's lower reaches.
The marine lock, loosely modelled on the 1980s' Thames Barrier in London, may be resurrected amid insurers' safety fears for Manhattan and Wall Street in the event of a Fukushima-style tragedy.
Another proposed barrier at Block Island Sound would link Long Island's Montauk with Mystic on Connecticut's southern shores to protect eastern waterways outside La Guardia Airport.
Both sites have been described as huge tsunami risks as new evidence linking seismic activity to solar and lunar eclipses was being studied by Pentagon geeks.
NASA satellite footage this week discovered the USO imagery just as a worldwide earthquake/tsunami warning was issued for the June 15 occultation.
Seismologists said today the tremor season had already kicked in with reported quakes in Christchurch, New Zealand rocking the Antipodes.
"We can't say for sure if this USO was the same one that triggered the erection of the Thames Barrier," a US Geological Survey source said today.
"It may just have been panning the Hudson bottom for gold!
"Seriously, though, the Narrows Barrier project may yet get kick-started...so long as nobody says Aliens Warn New York Will Sink."
Another marine tsunami barrier project outside San Francisco Bay may start taking shape following the 2012 White House presidential election outcome.