An "extensive" search operation was launched after screams for help were heard in the area under Laugharne Castle last night.
Police, fire, coastguards and the RAF were involved in the search after the alarm was raised at around 9pm.
The Sea King was scrambled to search from the air after the alarm was raised, while teams on the ground searched the foreshore area.
Eventually, after a three hour search, rescue teams stood down.
A coastguard spokesman said: “The Tenby and Llansteffan Coastguard teams, along with Dyfed-Powys Police, Mid and West Wales Fire and Rescue Service and RAF Helicopter Rescue 169 were involved.
“There was a report to the police of screams for help.
“There was an extensive search conducted by land and air units with nothing untoward found.”
He added the police took the initial call.