A helicopter was dispatched at 6:45 a.m. today to search the waters near the Tiburon peninsula after the Coast Guard received what sounded like a distress call Monday night.
The cryptic call came in over a marine radio channel at about 9:15 p.m.
"There was a female saying 'Listen to me, listen to me," followed by a pause, then 'hello,' another pause, and '10-4, I have mayday," Coast Guard Chief Petty Officer Donald Newton said.
The Coast Guard was able to approximate the woman's location and sent two vessels to search the Bay east of the peninsula. They scoured the water from the Richmond-San Rafael Bridge to Angel Island but the search came up empty, Newton said.
At first light today, the Coast Guard sent a helicopter from San Francisco International Airport to scan the Bay again, Petty Officer Pamela Manns said.
The Coast Guard chose to do an aerial search this morning instead of sending boats because the tide and currents created a drift pattern overnight that would have moved the possible distressed boater from her original location, Manns said.
The helicopter allowed them to search a broader area more easily, Manns said. The search was suspended at about 8 a.m.
"The fact is, there is no evidence that there is a (boater in) distress," Manns said.
She said any evidence that indicates there was actually a person in distress - even something as small as clothing floating in the water - could reinitiate the search.
"Anytime someone hails mayday over our channel 16, that's the same as calling 911 and saying you're having emergency," Manns said. "We always treat that as an emergency, we always respond, we always go out and search."
Newton stressed that it is important for troubled boaters to "include their position and the nature of the distress in the initial broadcast" so the Coast Guard can better assist their mayday call.