The real flood/catastrophe that nearly destroyed humanity?
Well no one survived but 8 people, and I think they had a few things to do while it was all happening. Accounts were passed on, thats why we have the story today.
Back to Krakatoa...
Not 8 people, but about 10,000, and not Krakatoa, but go a few hundred miles north-west and back in time about 70,000 years, and you've got a possible theory for the origins of some of the flood mythologies, especially as tsunamis could have reached eastern Africa, where many of our ancestors could well have been.
This would rely on the seemingly unlikely possibility of stories being passed down over 3,000 generations, but the Lake Toba eruption is the closest known thing to your scenario.
The Jewish tribal god, of course, couldn't have been involved, as he hadn't been invented at that point in time. ;)