Hi Phil. 8 meters away? Could you tell us about what angle you were to it? Above it? At the same depth? 45 degrees angle?
The reason I ask is that for years DM's have been talking about this "cone of aggression" where triggerfish tend to attack. Theoretically, the cone starts where the triggerfish is or where his nest is and spreads out as you go higher in the water column although I have heard other DM's swear the cone is the upside version of that too. The problem is that I have never heard marine biologists say this. Also, we get lots of titan triggers around where I dive so I keep a very close eye on them. We see them on average ab out every second dive. When they do attack, which is far to often for me, I'd say 80% of the time they chase other fish or humans away who are at the same depth or no more than on an angle of about 20 degrees upward. I've never seen them attack straight up but the other 20%, they have attacked from 20 to 60 degrees upward.
From personal experience too, I was attacked 3 times and never within the cone. Of all the other people I know who have been attacked, maybe 1/4 have been in the cone although I never have heard any dimensions of the cone so I am guessing. I have also hovered about 5 meters above a feeding (not nesting) trigger and while he kept an eye on me, he was not aggressive at all. Of the many fish I have seen attacked by triggers, they have all been along the bottom.
BTW, if the cone extends from 3 degrees upward to directly overhead, I take back everything I said.