Nothing seems to have happened to have set off the shark. We learned of no set of facts that we could use to avoid this next time.
Well if the 'rumour', and I have seen nothing to confirm this as fact, hence why I say 'rumour' for now, that the woman set off for the surface alone (or even with someone)
in a hurry, then that would be enough to set off a shark like the one described in this incident. Big sharks are unpredictable at the best of times, no matter what we might like (and hope) to believe. Seems it was simply an unfortunate accident, that when all the facts come out may include a tidbit of info that might, repeat
might, help to mitigate this occurring to you or I. Till then analyse the risk, accept (or not) the risk, and take appropriate precautions (which may be different precautions to different people) to mitigate the risk.
Most on this tread want the same thing: why and how can it be avoided.
Why? 'Something' set off the shark, or it just was 'out-a-hunting (anything) that day.
How can it be avoided? It can't, unless you stay away from sharks (and that's still no
guarantee) / or stay out of the water completely (which's is a guarantee, 'cept against the land shark variety). Every time you / I get in the water there is a potential for an accident. It's an alien environment after all. Add in some big big predators and it just got even more dangerous. Just because it never happened before / we haven't witnessed it happen ourselves, does not mean it won't happen. I think that many of us may have or had lulled ourselves into a state of mind that thought what we are / were interacting with was always going to be OK, because it always almost had been, or had been in our direct experience anyway. Or we just encouraged ourselves to believe the old 'it won't happen to me' reinforcement idea. And now that it has happened doesn't mean it wont happen again. The old adage 'lighting doesn't strike in the same place twice' has oft been proven wrong, unfortunately.
But glad you and your cohorts are still planning on going to Cocos, as would I if in your shoes! After all if your numbers up, your numbers up, at Cocos or simply walking the streets.