a secret one for fear

Here's what I don't get about this whole sea-parting episode: why on earth would an army think that following a horde of people through split water was a strategic move? Which part of the supernatural did they think was so commonplace that God wasn't involved? Which aspect of walls of water on their right and their left gave them any sort of comfort?

I imagine the Israelites were completely frightened they could pass through the split without harm -- and they believed they were chosen. The kind of fright passing through the Egyptians must have been even worse. Sure, Pharaoh was hardened, but what of the rest?