[numtel]

Exactly, I don't believe one bit that they're "attracted to the pressure differential of the prop." I've swam in the ocean and boats are extremely noisy and annoying underwater. The Orcas fully understand that the boats are linked to the changes in the ocean.

To the downvote: I'm sure you've heard a drone buzzing above your head and getting nervous. A boat propeller does the same thing.

[hansendc]

There's at least one extremely well documented example of a killer whale that played extensively with boats: https://en.wikipedia.org/wiki/Luna_(orca)

Granted, this was a lonely little fellow. But, he knew perfectly well what he was doing and repeatedly approached boats, despite the noise. He died after colliding with a tugboat prop.