An underwater robotics specialist is revealing a "shipwreck city" hiding beneath a lake in a major West Coast hub - and much of it remains a mystery.
Remotely operated vehicle (ROV) specialist Phil Parisi is working to verify and document nearly 100 "targets" in Lake Union, a central lake in Seattle, Washington.
The urban lake has served as a working waterway for over a century, supporting shipbuilding and vessel traffic in the Emerald City.
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The expert told KING 5 that about half of those sites, which were previously mapped but not visually confirmed, are believed to be shipwrecks - and not all of them have been explored by divers.
To bridge that gap, Parisi uses ROVs to document targets identified in sonar surveys.
"We need to document what these wrecks look like today," Parisi told KING 5.
He described deeper portions of the lake as a "ghost town," where plant life drops off beyond about 25 feet.
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"There is a harsh lack of life," Parisi said.
But what the lake lacks in marine life, he said, it makes up for in wreckage.
"It's crazy that there's so much down there," he added, according to KING 5. "It's shocking to me. I was stunned. Looking at these maps - it's shipwreck city."
Parisi told Fox News Digital that, while roughly 40 sites have already been documented, dozens more identified in sonar surveys have yet to be visually confirmed - work he is now taking on.
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Parisi and his team use GPS to get close to targets, then rely on sonar to locate them in low-visibility waters.
"Flying blind through murky, low-visibility waters is difficult, so we rely on ROV-mounted sonars to 'see' and determine the target's relative position," he said.
"Then, we descend to the bottom and fly toward the sonar signature until the target appears on the live ROV camera."
Because of pollution in Lake Union, Parisi said his team relies on ROVs rather than scuba divers.
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"It's nice not having to worry about contaminants," he said.
But they still face challenges, particularly with Seattle's piers lining the lake.
"Many wrecks are tucked underneath, and some marina owners are reluctant to let us film beneath their docks," he said.
"Additionally, when we do arrive at a wreck, gathering identifying information can be extremely difficult. Biofouling, rust, poor public anchoring techniques and other environmental degradation often shed registration stickers, obscure painted hull names, and cause wrecks to collapse."
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Asked about describing the lake as a "shipwreck city," Parisi said two things stand out about the underwater sites: the shallowness of Lake Union and the large number of "unknown" targets that remain.
"The lake is surprisingly shallow compared to other bodies of water in the Puget Sound, meaning lake goers are a stone's throw from the sunken maritime history yet are often unaware," said Parisi.
"Secondly, documentation or footage is missing for over half of the nearly 100 targets in the lake, leaving a huge gap in our understanding of what's down there."
Parisi said the work isn't a new discovery, but builds on earlier sonar surveys and dive records that mapped the sites.
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He also stressed the importance of local exploration, saying he wants Americans "to be excited about what's in their own backyard."
"Every place holds incredible landmarks and hidden treasures, yet we're often distracted by the humdrum of life," said Parisi.
"When you get the chance, allow curiosity to take over and do a deep dive into your local city or town's history - it is amazing what happened not so long ago, and it never disappoints!"
