I think these are attacks by a population that's starving to death, surrounded by deafening noise (and remember, their primary sense is hearing) and poisoned by heavy metals accumulating in the food chain. I think they understand that humans and boats are responsible for the stress they're experiencing, and are attacking smaller boats that they think they can sink in desperation or anger, similar to how Tilikum snapped one day and killed Dawn Brancheau.

The southern residents of the Pacific Northwest are the most studied population of wild of orcas in the world (actually, they're probably the most studied population of wild mammals). They seem to have a lot of similarities to the Gibraltar orcas- both seem to eat fish exclusively, and in fact heavily specialize in one large fish species (Chinook salmon for the southern residents, bluefin tuna for the Gibraltar orcas). Both populations appear heavily stressed due to human activity, especially food loss due to fishing, and both have experienced a crash in successful pregnancies. In the southern residents, two years ago this led to Talequah making news by carrying her dead calf for two weeks over hundreds of miles, seemingly in mourning. I think these attacks are also basically emotional and based on a correct general understanding of how boats are affecting them, and not especially different from what humans would do in a similar situation.