A body has been found in the Llansteffan estuary after reports of a man getting into difficulty in the water.
Emergency services were called to the area about eight miles south of Carmarthen at around 3am on Tuesday.
A huge search and rescue operation is still underway to find anyone else who could be in the estuary.
Police said it is not yet clear whether anyone else entered the water with the man.
Officers confirmed the man died but no further information has been released about his identity.
Fire and rescue teams and the Coastguard were also in attendance, with a large number of emergency services still at the scene.
Dyfed-Powys Police is appealing for information from any potential witnesses who may have seen what happened.