It says in the Gemara that Hashem made a condition with the sea at the time of creation that it should split. The deeper meaning is that AFTER the primordial sin, the world is guided with הסתר פנים - In a hidden way, in order to enable free choice. Before the sin, there was גילוי פנים - a revealed way of guiding creation.
So in the period of גילוי פנים, Hashem made a condition enabling Him to display His revealed powers even during the period of הסתר.
[ואני תפילה]
