If the water has any movement or force to it, you should absolutely never, ever walk, ride, or drive through it. A few inches of water can easily move a car off a road. A bike has much less of a contact patch with the ground so it may not be affected as much, but it's still stupid dangerous.

If the water is not moving, I still wouldn't go through it for the simple fact that you can't see what hazards lie beneath - road could be washed out, could be large holes, debris, etc. It's just a dangerous proposition all the way around. Flood waters are nothing to play with.