The cousin of the person who was swept away notified park officials and then rangers reported the incident to the Coast Guard at 12:50 a.m. and a search effort was launched, Petty Officer Jonathan Cilley said.
A Coast Guard helicopter from Air Station San Francisco arrived in the area at 2:09 a.m. and a 47-foot motor lifeboat from their station in Monterey arrived at 5 a.m. to search for the missing person.
Firefighters from Big Sur were searching area beaches along with state park rangers to see if anyone washed ashore, Cilley said.
As of about 8:30 a.m., no one had been located, he said.
The park, which is 2 miles south of the unincorporated Monterey County community of Lucia, is off of state Highway 1.