What Great Fish Swallowed Jonah?

Both the Hebrew and the Greek versions of the Book of Jonah do not specifically say Jonah was swallowed by a whale, but that he was swallowed by a ketos, which in Greek means "great or large aquatic animal". This could mean either a whale, a shark, a sea monster, or even some sea creature specifically created by God to serve His purpose. Whole animals as large or larger than a man have been found in the stomachs of the sperm whale, the whale shark and the white shark. St. Nikodemos the Hagiorite explains in his Synaxaristes the possibilities of what the ketos described in the Book of Jonah could be:

Saint Anthony's Encounter With the Satyr and the Centaur

In the Life of Paul the Hermit by Saint Jerome, written in the year 374 or 375 during Jerome’s stay in the desert of Syria, we read how Saint Anthony was on a journey in the desert to find Saint Paul of Thebes, who according to his dream was a greater and more perfect desert-dweller than he. Saint Anthony had been under the impression that he was the first person to ever dwell in the desert; however, due to the dream, Saint Anthony was called into the desert to find his "better," Saint Paul. On his way there, he ran into two creatures in the forms of a centaur and a satyr, which are considered to have been demonic temptations, although Jerome seems to be open to the possibility that they may have been monstrous creatures of the desert, of which he says that one such creature was seen alive in Alexandria during the reign of Constantine the Great.

Saint Columba and the Loch Ness Monster

The event described below by St. Adomnan (c. 690) in his Vita Sancti Columbae is said to have happened in 565 AD:

Concerning a Certain Water Beast Driven Away by the Power of the Blessed Man's Prayer

Also at another time, when the blessed man was for a number of days in the province of the Picts, he had to cross the river Nes [Ness]. When he reached its bank, he saw a poor fellow being buried by other inhabitants; and the buriers said that, while swimming not long before, he had been seized and most savagely bitten by a water beast. Some men, going to his rescue in a wooden boat, though too late, had put out hooks and caught hold of his wretched corpse. When the blessed man heard this, he ordered notwithstanding that one of his companions should swim out and bring back to him, by sailing, a boat that stood on the opposite bank.