Revenge of the orcas? Killer whales have sunk 3 boats in unusual attacks.

A spate of encounters between orcas and boats off the Iberian coast has puzzled scientists and sailors recently, as seemingly coordinated ambushes by the killer whales led to the sinking of three vessels. The reason for the attacks, according to one scientist who has studied the phenomenon, may be revenge.

The leading theory is that a female orca suffered a traumatic incident with a boat — a “critical moment of agony” — that caused her to start attacking the vessels, Alfredo López Fernandez, a marine biologist at the University of Aveiro in Portugal, told the industry publication Live Science.