Millions of small dead jellyfish-like creatures have been blown ashore on to a Carmarthenshire beach.
The Velella velella, commonly known as By-the-wind Sailors, litter the tide line as far as the eye can see along seven miles of sand at Pendine.
They are blue, measure up to 10cm (4in) and although they have a small sting, are harmless to people.
Experts say there is debate that climate change is sending them further north than they used to go.
They are relatives of the Portuguese man-of-war, and are classed as colonial hydroid and not jellyfish which they resemble.
Cliff Benson of the Sea Trust, which monitors marine life off the west Wales coast, said while rare, they were becoming more common.
"They are amazing things that have a sort of sail on their back and live on the surface of the sea," he said.
"They can be found in their millions and millions if not billions in the Atlantic.
"Two or three years ago there were a lot washed ashore - it does not happen every year and they are a bit of a phenomenon.
The jelly-fish like creatures grow up to 10 cm (4in) long
"To me this seems late in the year to see them, but I suppose the prevailing winds have been quite strong and I suppose they'll have been blown into the Bristol Channel."
They live on the surface of warm seas throughout the world and feed on plankton.
They measure up to 10 centimetres and are blue in colour and from a distance look a bit like a mussel.
They do have a small sting to capture their prey but most humans would feel only a tingle if they had sensitive skin.
"They are harmless - they are not going to hurt anyone," added Mr Benson.
He said there was speculation and debate that global warming meant they could now be found further north.