The mechilta asks on the following psukim in the Shirat HaYam (Shemot 15:8-10):
I would suggest that what is happening here is actually pluperfect. Rather than "the enemy said," it is "the enemy had said." That is, pasuk 10 echoes or continues pasuk 8, and pasuk 9 it stressing the greatness of God and the ineffectiveness of man when faced with divine power. They had said they would accomplish all of the following (pursuing, dividing spoil, etc.), yet God just blew His wind and the sea covered them, and they sank as lead in the mighty waters. So the pasuk is in chronological order. (The same point of the intent of the pasuk would apply even if it is the normal perfect.)
Yet, the question itself seems silly. We are talking about a song! Of course things may be out of order in a song - the purpose is praise, not mere recounting of events.
I would say that that may be exactly the point, and exactly the meaning of אין מוקדם ומאוחר בתורה in general, in the thought of Chazal. The Torah is called Shirah, song, and its purpose is praise, not necessarily historical narrative and recounting of events. Just as we would not demand chronological order in a song, it is no big deal if the Torah's recounting of events deviates from chronological order.