I copied this from a Christian site ( lost the link), but it’s interesting for Muslim readers as well:
“The… reason why we should believe the account of Jonah is because even extra-biblical sources affirm its possibility.
“This is the summary of the Encyclopedia’s report on Jonah. The report theorizes that the “great fish” was most likely a sperm whale. While the common Greenland whale could scarcely swallow an orange, the sperm whale has a mouth that averages 20 feet long, 15 feet high, and 9 feet wide. It is well known that the sperm whale feeds largely on squid which, of course, are much larger than humans.
“As to whether a man could survive in a whale’s stomach, the Britannica article maintains that one certainly could, though with great discomfort. The report maintains that there would be sufficient air to breathe–air that is necessary for the whale to float. The temperature inside the whale would be great, but bearable at about 104 – 108 degrees F. There would be unpleasant contact with the whale’s gastric juices, but these juices could not digest living matter.
“You may even be surprised to hear that Jonah is not even the only human to ever survive such an ordeal. During a voyage of a whaling ship in February of 1891, a sperm whale was spotted and pursued in the vicinity of the Falkland Islands. In an attempt to harpoon the whale, one sailor drowned while a second one disappeared. Eventually the whale was killed and drawn to the side of the ship where it was dissected.
“The next day, the stomach was hoisted on deck and opened–with the missing sailor lying inside. The sailor was unconscious, but alive. He was eventually revived and, after a time, resumed his duties on board the whaling vessel(Wilson, Sign of the Prophet Jonah, 630 – 642). “