Your best defense would be to explain that a crazy driver forced you into deep water, by trying to avoid a collision. If water got inside the cylinders, that could have bent the rods. If you drove the car home without any noise in the engine, it would be strange that it is now a problem. The 1st logical step would be to remove the spark plugs, to see if moisture is in the cylinders.
I would think that a rebuilt motor installed by anyone, would be between 6k to 10k for the repair.