I'm pretty sure I read somewhere that (wild) killer whale attacks on humans are very, very rare and no deaths have ever been recorded. That being said, I think an encounter like that would have scared the shit out of me too.
Also, did you notice that when the Orca was under the boat he was upside down and looking up at the boaters. That was cool. He was checking out the boaters and they were checking out him/her.
It reminds me of when I was a kid and we were transferred to Barksdale AFB in Louisiana. The first time my dad and I went fishing in a canoe on Flagg Lake a big ass gator came swimming towards us. I just knew that thing was coming to tip the canoe over and eat us, LOL! Instead it disappeared under water and popped up on the other side of the boat about 10 feet away. It had no interest in us at all.