THIS MIGHT SURPRISE YOU
The answer
There were two fish. In Midrash Jonah a male fish swallows Jonah first, and its belly is roomy and comfortable. Jonah does nothing there, so he is moved into a female fish, and there he prays.
Why it’s interesting
The female fish was pregnant with 365,000 little fishes, which is why it was so crowded. A synagogue mosaic at Huqoq from the fifth century AD may show a chain of fish as well: one swallowing Jonah, a larger one eating it, and a still larger one eating that.
Scholarly consensus
Learn the Bible.
Not just the stories, but the history, authorship, and scholarship behind it.