'A whale,' as in Jeremiah 51:34, signifies people who possess the universal aspects of the knowledges of faith, as known, and apply them to evil purposes. 'Whales,' or 'great fishes,' are sometimes mentioned in the prophets, and are used to signify the universal aspects of knowledges

(References: Arcana Coelestia 42)

The number "four" in the Bible represents things being linked together or joined. This is partly because four is two times two, and two represents the ultimate linking between our desire to be good and our understanding of truth. We can also see this in the fact that most buildings are rectangular, with the four sides linking together to make a whole. We also divide directions into four -- north, east, south and west -- and talk about the "four corners" of something meaning all of it. So our special thinking naturally looks at four sides as linking together into a whole.

(References: Apocalypse Explained 417; Arcana Coelestia 1686, 9103, 9601, 9767, 9864)