Not what you want to hear, but draining the pond down so you can work on the holes is probably the most reasonable way to keep this from happening again (maybe in ten years when it lets loose again), so you can add concrete around them). Alternaitvely, salvaging what you can and making this a floating dock might work (as suggested above). If the dock can be reset without draining the pond, you might want to consider if the posts could be weighted with concrete, rocks or metal, so this won't happen again. Chaining the posts to heavy chunks of conrete located under the dock (so divers won't clunk their heads) might be an inexpensive solution. You may get lucky and it will settle back into place (or close enough). This is a real bummer, but a lot of folks have swimming pools in their baseements, so it could be a lot worse.