“They seemed more aggressive/playful when we were sailing at speed. Once we slowed down they also started to be less aggressive in their attacks”

This is an interesting detail. It definitely supports the leading theories, that either they’re playing (chasing fast moving things is more fun) or reacting defensively after the pod experienced a ship collision.

Orcas are afraid of literally nothing. They can eat great white sharks and blue whale calves. The only solution here is probably to explore something as a nonlethal deterrent, like spikes on hulls/rudders or an underwater klaxon.