Lu Jingwai, who filmed the scene, said the sheer volume of small fish made the sea resemble “boiling water.”
Footage posted on his Facebook page showed a huge number of the shiny creatures jumping from the water, some landing on his boat, in the Basha fishing port in Keelung, Taiwan.
“It is so scary! I am being attacked by fish!” Mr Lu said in the video.
He told the Daily Mail the fish had likely fled to the surface after sensing a threat, and could possibly have been chased by barracudas.
“I’ve seen three to five barracudas over a metre (3.3ft) long swimming under my boat two days ago,” he said.
“I guess it is their hunting season these few days.”
Several members of the public had reported seeing barracudas near the fishing port on the same day, SETN.com reported.