"before Ba'al Tzefon": Only Ba'al Tzefon remained of all their idolatries. "Over against it shall you encamp by the sea": to deceive the Egyptians into believing that it had rescued itself, viz. (Iyyov 12:23) "He deceives (homiletically, "mashgi") the nations to destroy them."
Before Ba'al Tzefon Only Ba'al Tzefon Remained of All
Mekhilta Tractate Vayehi Beshalach 2:5