Had exactly the same happen to me yesterday Tiffer. Rather annoyingly it was in our monthy CC Championship and I would have come in with the joint-lead score. However, one trip in the pond after a nice bit of lag led to a triple bogey and a throughly average score.
As to where the drop is, it must be the first droppable point in line with entry to the water. As Dustin Johnson found out at Whistling Straights, sand is everywhere on this type of course. You'd have thought WGT could have found a slightly nicer lie though rather than punish you further for ending up in the drink.