Investigators say 60-year-old Michael Healy was last seen swimming with his boogie board Wednesday morning.
His boogie board was found between the Bonner Bridge and the Marc Basnight Bridge.
Emergency crews searched for Healy for more than 16 hours Wednesday, covering 43 nautical miles, but they suspended the search Wednesday night.
Rangers with the National Park Service are continuing to patrol the shoreline.
Anyone at Cape Hatteras National Seashore is asked to call 252-473-3444 if they have information that could help locate the missing swimmer.