What's under the crystal bridge in Asgard?

I noticed something the other night as my kids were watching Thor. Every time they show the crystal bridge leading to the Bifrost chamber, it's got flowing water underneath it. The water flows right up the edge of where the chamber is and then falls off into the void of stars beneath Asgard.

At the end of the film, Thor and Loki are fighting on the crystal bridge, and they're a good distance from the Bifrost chamber - probably 30, 40 feet or more. However, when Thor starts smashing the bridge and Loki falls off one side, he's suddenly hanging above the starry void and NOT flowing water.

Is this a continuity snafu within the film or did I miss something? How did that portion of bridge get the void under it and not water?