For the first time, images of the worst shipwreck in San Francisco history have been revealed, shedding some light on this maritime mystery.

More than 100 years ago, the SS City of Rio de Janeiro struck jagged rocks near the Golden Gate Bridge and sank to the bottom of the bay, taking 128 passengers and crew with it. The steamship, often called the "Bay Area's Titanic," was carrying Chinese and Japanese immigrants as America expanded into the Far East and Pacific after the Civil War.

The NOAA, who is involved in a two-year study to discover and document shipwrecks in the San Francisco area, found the historic wreck 287 feet below the surface of the San Francisco Bay, buried in mud.

The whereabouts of the City of Rio de Janeiro have been known for some time, since the 1980s when salvagers first found the sunken ship, however the lack of accurate coordinates kept the exact location of the site somewhat a mystery.

That is, until the NOAA teamed up with Hibbard Inshore and Bay Marine Services to find the wreck once again, this time using a remotely operated vehicle and sonar developed by Coda Octopus. Their fruit of their labor provided the first detailed sonar and 3-D images of City of Rio resting in the dark, muddy waters outside the Golden Gate Bridge.

The team also found another shipwreck, of the S.S. City of Chester, which was rediscovered last year.

"The level of detail and clarity from the sonar survey is amazing," researcher Robert Schwemmer, who helped lead the expedition, said in a statement. "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."

To date, the NOAA's Office of National Marine Sanctuaries Maritime Heritage Program has plotted nine of nearly 200 ships, including four never before found vessels, looking back in time to when these ships were once afloat.

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