The raft was later found 5 miles down the river lodged in mudflats.
“It was quite embarrassing ringing the coastguard about this,” said Mr McCue.”The coastguard I spoke to was in hysterics for about 10 minutes when I told him.”
Mr McCue said that people in the town had told him the mannequins, which are dressed in Scottish rugby shirts, kilts and wear masks, looked very lifelike from around 25ft away.
“Anyone spotting it from a distance may have thought there were people in trouble on the raft,” he said.
The 25ft monster raft is to be the centrepiece of the Carmarthen River Festival in west Wales next month.