Beshalach - Tefilla and Action

Bnei Yisrael are standing at the Sea, and they see the Egyptian forces coming. They call out to God, praying. Moshe tells them that God will fight for them, and that they are to proceed. How are Bnei Yisrael supposed to go if Moshe has not yet been commanded to split the sea? And how are we to understand the predicament of “Moshe’s hands were heavy” during the war with Amalek?  And where does the story of the manna fit in? We find some interesting parallels to Korban Tamid. The connections between the successive stories in Beshallah, model different aspects of the idea that God demands tefilla combined with action.