In my recent video about Jonah and the Great Fish, I used a great white shark in the thumbnail for the video. Here’s the thumbnail:

The book of Jonah does not identify the species of fish that swallowed Jonah; heck, the Hebrew doesn’t even distinguish between fish and whales, as modern people are obsessed with doing. Realistically, how important is it that whales nurse their young with milk? Is anyone planning to try keeping dairy whales?
How we think of the great fish that swallowed Jonah has a real impact on how we think of the story, though. I think a lot of people think of it as a baleen whale, which makes them think of it as a relatively comfortable experience. Something like this:

And, admittedly, the fin whale, the second longest whale in the world, does live in the Mediterranean sea. There’s a real problem with this version of the story, though—baleen whales are designed to eat krill, not large things. The blue whale (which doesn’t live in the Mediterranean) has an esophagus that is normally around 5 inches in diameter and may be able to expand up to about 10 inches in diameter. That couldn’t fit a child of ten, to say nothing of a grown man.
There is a cetacean option for the big fish in the Mediterranean, but it’s not a comforting one: sperm whales. Sperm whales have a lot of teeth and they are best known for using them to kill giant squid half a mile or more under the sea. To be fair, they probably do use suction to pull food into their throat but we’re not talking about gentle suction. If you’ve ever been hit by even a moderate size wave, you have a sense of just how much water suction can rip limbs off of a body. No matter which plausible enormous sea-dwelling critter you consider as the great fish that swallowed Jonah, merely the swallowing itself will normally kill you.
I don’t want to get into the argument over whether Jonah died and was resurrected on the third day—that takes too long here, and I went over it in the video—but I just want to emphasize that even if you really want to hold that Jonah miraculously survived being eaten by a great fish and being in its belly for three days rather than Jonah dying and miraculously being brought back to life, appreciating the degree to which Jonah should have died is necessary to understanding how miraculous the story really is.
If you’re interested in the video, here it is: