The book of Jonah does not name a species. It says the LORD appointed “a great fish” to swallow Jonah Jonah 1:17.
In Jonah 1:17 the narrator describes an immediate, surprising turn after Jonah is thrown into the sea. This verse concludes the sea-escape episode in chapter 1. Jonah has fled his commission, a storm has exposed him, and the sailors have thrown him overboard; the sea then calms, showing the crisis has shifted from the ship to Jonah himself.
The verse presents Jonah’s survival in the sea as God’s direct intervention. The narrator says Yahweh “appointed” a “great fish,” and that fish “swallowed” Jonah. Jonah’s location is described plainly as “in the belly of the fish,” and a specific time marker is given: “three days and three nights.” These are explicit claims in the text, not implied ideas.
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with Jonah 1:17, then read the surrounding section so the answer stays connected to the passage's flow.
17Yahweh prepared a great fish to swallow up Jonah, and Jonah was in the belly of the fish three days and three nights.