I don't know much about it BRL, but I do seem to remember this comming up here or possible on the flyer site, a couple of months ago.
I think the answer was something to do with the Citation engines being left in the "on" position. I think if the engines quits while in the "on" position, there is some sort of auto restart. As I remember the explination it was likely that the engines constantly tried to restart, but couldn't because of the water, but when the passengers exited, it probably allow the aircraft to rise just enough to allow the engines breath enough air to restart.
I'm sure Chilli will know much more, and be able to put you straight
If not, a search here or over the other side, might reval the thread that I'm remembering.
dp