Beachgoers have been caught on camera fleeing in terror after mistaking a pod of beached whales for a shoreline shark attack.
The video, filmed at Prainha beach in in Arraial do Cabo, Brazil, shows a number of people on the beach fleeing and screaming in terror as they see dorsal fins and huge tails trashing around in the water.
The water turns dark as the sea creatures churn up the sand on the sea floor.
It appears from the footage, which was taken on Saturday, December 31, that the beachgoers thought they were in the midst of a shark attack.
But experts have since revealed that the panicked swimmers were almost certainly swimming away from a group of harmless whales.
Biologist Marcelo Tardelli told Brazilian media the species seen in the footage is probably the dwarf sperm whale (Kogia sima).
A town hall spokesperson said: "If confirmed, it is the first time this whale has appeared in Arraial and it is considered a rare species, being an important record for science."
Some believed the white markings could identify the whales as harmless hourglass dolphins.
When officials later inspected the beach, they found no beached whales and said the sea creatures likely managed to swim back out to sea.
They confirmed the animals were toothed whales (Odontoceti) and not sharks as some beachgoers had thought.
In the footage, some witnesses seemed to be trying to help the stranded marine mammals.
But the Fundacao do Meio Ambiente (Environment Foundation) said people should avoid approaching or touching stranded animals.
It said: "In these cases, the most advisable thing is to wait for the arrival of specialised teams to help the animal."
Authorities said there was a massive stranding of dolphins in the same location in 2012.
Late last year the Mirror reported on the beaching of a mammoth 63st pregnant whale which washed ashore on a shore in Taiwan.
Rescuers managed to save the pygmy sperm whale which was found alongside a youngster believed to be its offspring.
The pair were uncovered in the Yong'an fishing port along the coast of Taoyuan City on Saturday.
Members of the Taiwan Cetacean Society tried to save both whales, but the younger sadly died at the scene.