The sea, and waters in particular, represent the collective souls of men
and their interactions with each other. When the sea is stormy you have
great turmoil, like in a frenzied mob. When you proclaim the gospel to
the unsaved their souls are agitated, many are angry. This is
represented by a stormy sea. It is general bible allegory.
Yam Suph is the Reed Sea, so-called because of it's elongated reed-like
shape. In this case it is an allegory of the passions of the Egyptians
against the Israelites. God will suppress and hold back the passions of
man from doing any real harm to a believer who calmly walks on to the
other side of the turmoil without getting caught up in it himself. If a
man allows himself to be caught up in the passionate emotions during
controversy or strife, he will be walking in the flesh and no longer be
walking according to the spirit and will be doomed to be a part of the
strife and will sin too.