In 1901, the SS City of Rio de Janeiro, an iron-hulled steam-powered passenger ship, was gashed by an underwater reef at the mouth of the San Francisco Bay, not far from the Golden Gate Bridge. The ship was en route from Hong Kong.

The vessel sank and of the 210 passengers and crew on board only 82 survived -- 128 perished. Most consider it the worst accident in San Francisco's maritime history.

Until now, few have documented the wreckage. But this week -- after a month-long expedition -- researchers with the NOAA unveiled the first-ever 3-D imagery of the sunken ship.

NOAA used sonar to locate the ship, while two local companies, Hibbard Inshore and Bay Marine Services, donated a vessel and crew to help carry out the research. They also donated a remotely controlled submersible to advanced imaging instrumentation.

Because what's left of the ship is mostly buried in mud -- and some 250 feet of cold, murky water -- only the sonar imagery offers a decent view of the defeated hull.

"The level of detail and clarity from the sonar survey is amazing," Robert Schwemmer, West Coast Regional Maritime Heritage Coordinator, said in a press release. "We now have a much better sense of both wrecks, and of how they not only sank, but what has happened to them since their loss."

There are no plans to salvage the wreckage.