According to Moses, God helped the Israelites by making a path through the sea so they could walk safely with big walls of water on each side. This showed that God was protecting and taking care of His people.
Exodus 14:29: But the children of Israel walked upon dry [land] in the midst of the sea; and the waters [were] a wall unto them on their right hand, and on their left.
The contradiction with that event might be the parting of a large body of water, which goes against the laws of physics as we understand them today. Water naturally seeks to fill available space and does not stand upright like two walls without a physical barrier or force we currently know that can hold it in that formation.