The orcas are at it again.

A group of the highly social marine mammals, also called killer whales, attacked and sank a 50-foot-long sailing yacht on Sunday, the New York Times reported. Two people had to be rescued from the waters near the Strait of Gibraltar.

The incident was yet another in a startling spate of such attacks by orcas (Orcinus orca) in the area since 2020—an apparently emerging phenomenon that has researchers stumped.

“It is a rare behavior that has only been detected in this part of the world,” said Alfredo López, an orca researcher at the Atlantic Orca Working Group (GTOA), in an interview with Scientific American last year.

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