The Red Sea
A pillar of fire by night, the sea standing up on either hand, and a way through it. Scroll to watch it.
But God went before them by day indeed in a pillar of cloud, to show them the way; and by night in a pillar of fire.
Exodus 13:21, as St Cyprian of Carthage gives it
We will sing unto the Lord, for He is to be gloriously praised; the horse and his rider He hath cast into the sea.
Exodus 15:1, as St Athanasius of Alexandria gives it
Nothing else then the passing through the sea did signify, but the Sacrament of the baptized; nothing else the pursuing Egyptians, but the multitude of past sins. Ye see most evident mysteries. The Egyptians press, they urge; so then sins follow close, but no farther than to the water.
Augustine of Hippo, Expositions on the Psalms LXXXI