A television news station's helicopter spotted the sunken vessel off of Sausalito and notified the Coast Guard around 12:30 p.m., Lt. Jon Lane said.
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The boat has a salvage buoy attached to its stern and it's possible the owner expected the vessel to sink, Lane said.
"It looks like an older boat without bilge pumps to remove the water from the heavy rains," Lane said.
The Coast Guard's incident management division was alerted and is trying to contact the owner, Lane said.