Mysterious footage, filmed on Sunday, shows thousands of fish washed up on a beach in Marazion, Cornwall.
It's the second time this has happened in a month and no one is 100 per cent sure why.
See also: Mysterious barnacle-covered object washes up on NZ beach
See also: Why have thousands of dead fish washed up on Cornwall beach?
It has been speculated by marine biologists that they were driven to shore by a predator.
However the BBC reports that some experts have suggested it may have been due to fishing boats releasing part of what they catch.
This may happen when fish are released from the bottom of a net but sadly die anyway.
Katrina Slack saw the fish-covered beach and said: "I've never seen anything like it. It was like the waves were made of fish."
Another similar sighting occurred just a few weeks ago on another Cornish beach, the Guardian reports.
The Cornwall Inshore Fisheries and Conservation Authority's (Cifca) principal enforcement officer told the Guardian: "It's likely that the fishing in that area has been the cause of the problem."
According to All About Cornwall Marazion is one of the oldest market towns in Cornwall and the area boasts unspoiled views of St Michael's Mount, just off the coast.