“God my King is from ancient times, performing saving acts on the earth. You divided the sea with Your strength; You smashed the heads of the sea monsters in the waters;” (Psalms 74:12–13 HCSB)

We come to a passage like this and scratch our heads and ask ourselves: “What did the psalmist mean?  Did he really believe in sea monsters?”  We can only conjecture since we do not have the author here to query.  It is certainly true that the ancient Hebrews had little knowledge of the seas along with all other men so it is easy how they would think of what is under the seas as dark and foreboding and full of unknown sea creatures, which in fact it was.

I like the Tyndale Commentary here:  “The point here is that what Baal had claimed in the realm of myth, God had done in the realm of history – and done for his people, working salvation.”