"Great Fish" / "Whale" controversy

"...some critics argue that the book of Jonah depicts the prophet as

being swallowed by a “great fish” (Jonah 1:17), while the New Testament suggests that the creature was a “whale” (Matthew 12:40). And, as any schoolboy knows, a whale is a mammal, not a fish.
The fallacy of this ill-conceived argument lies in the fact that both the Hebrew word dag, and the Greek word ketos, are generic terms that can apply to any aquatic creature. There is no error here."
WayneJackson