Coast Guard and Navy crews are searching for a possible person in distress near the Ponce de Leon Inlet.
The Coast Guard began searching after hearing a Mayday just before 5:30 p.m. on Thursday.
Watchstanders monitoring radio calls attempted to communicate with the caller, but they received no response.
A Navy airplane crew says they also heard the call and began searching for any vessels in distress.
So far, no one has been found.