...splitting the matzah is a memorial to the splitting of the sea...
Although land and sea creatures are equally dependent upon their environment, the land creature can forget about the nourishment it receives from the earth, whereas the sea creature is constantly aware of its obvious dependence upon the water.
Man possesses both a land and sea personality. There is a part of man that is disconnected from his purpose and source: a "land" self that is oblivious to the fact that his soul is a spark of G‑d above; that he is granted life anew, every moment , by his Creator; that his existence has meaning only in the context of its role in the divine purpose.
Man also possesses a "sea" persona. When this self is manifest, the person is like a fish in water, his every living moment is an attestation to his utter dependence upon, and devotion to, his source of nourishment and life.
The ultimate challenge for man is not only to be a fish, but to be a fish in the midst of the land.
For when we submerge ourselves within the sea of the divine reality we can harness our ego and individuality to optimally realize our mission in life.
When the sea split, the Jews walked on dry land within the sea, a precedent that directs our quest for that perfect synthesis of land and sea which will be fully realized in the messianic age, when the land shall be filled with the knowledge of G‑d, as the waters cover the sea.