Leviathan - liv-ya-tan - is the Hebrew version of Litan, which is a Canaanite god that was an enemy of Baal. It was not a physical thing like a dragon.
In the old testament, Leviathan appears in multiple places and is one of the tannin -- which comes from the Ugaritic "tunnanu" meaning "serpent", and these were also Gods that were enemies of Baal(1):
Ugar. tunnanu as “serpent.” In the mythological literature of Ugarit,
the tunnanu appears in two texts as an opponent of the storm-god Baal
and his consort Anat. One7 describes the tunnanu together with yammu
and nahar and other mythological beings as enemies of Baal vanquished
by ʿanat, who muzzles the mouth of the tunnanu.8 The other9 describes
the tunnanu and arš as denizens of the sea.10 These texts may allude
to a calm sea voyage, which is associated with the craftsman-god
Kothar-u-Khasis, Baal’s ally,11 who drives away the sea monster.12
Behind the motif of enmity between the storm-god and a serpent stands
the Old Hittite Illuyanka myth,13 which originally described the
victory of the serpent over the storm-god and a subsequent defeat of
the serpent by the weather-god.14 Illuyanka is a precursor of ltn and
tunnanu.15 Even closer to the Ugaritic myth is the Hurrian Kumarbi
cycle,16 which is dominated by the antagonism between the gods Kumarbi
and Teshub. Kumarbi, who belongs to the old generation of dethroned
gods, has lost his kingdom and battles the storm-god Teshub with the
aid of the sea. The mention of Mt. Hazzi (Zaphon) in the Song of
Ullikummi,17 which belongs to the Kumarbi cycle, places it in northern
Syria. The motif of the battle between the storm-god and the sea
appears for the first time in one of the Mari letters,18 with
reference to Hadad of Aleppo. The battle between the storm-god and the
serpent represents a later development of this motif.19 In the Mari
letter the context for the motif of the battle between the storm-god
and the sea is a king’s seizure of power, a context that can be traced
subsequently at Ugarit20 and in the OT.21 The tunnanu appears in
magical texts as well as in mythological literature. The first three
lines of a collection of magical formulas22 call on Baal to destroy
(mḫṣ) the tunnanu and collect (?)23 the arrows of Rashap. This marks
the beginning of the demonization of the tunnanu. A spell in another
text also refers to Baal’s battle with the tunnanu.24 The mention of
the tongues (dual?) of the tunnanu shows that it had more than one
head,25 and the mention of tails (dual) indicates that it had one (or
several) pair(s) of tails.26 Here too27 the tunnanu is muzzled.28
In the Bible, these gods were associated to Israel's enemies, Egypt and Babylon and were associated to the sea, hence some translations use "sea dragon", "sea monster", etc.
Like all gods, they are not corporeal, but like other texts that describe how YHWH humbles and overcomes the gods of Israel's enemies, so also these passages show that God controls Leviathan and all of the tannin. What makes the tannin special is that in the Genesis account, God is described as creating them on Day 5:
Genesis 1:21 (LEB)
21 So God created the great sea creatures[tannin] and every living
creature that moves, with which the waters swarm, according to their
kind, and every bird with wings according to its kind. And God saw
that it was good.
The Masorah of Genesis 1.21 is interesting for two points, as it splits the verse into two disjoint Athnah, the first with the sea-monsters and the second with the rest of the verse. This has has interpretive effects:
- The tanninim do not move, e.g.
(God created the tannin), and (God created every living creature that moves..). as both are under disjoint Athnah.
Thus the tannin are not corporeal - they do not move or swim through the sea.
- God excluded the tannin (and only the tannin) from being
*(God created the tannin), and (God created every living creature that moves.. and it was very good):
Thus this is the only place in the Genesis account where anything that is not good is created, but the overall creation is very good, because the tannin serve God's purpose just as Egypt and Babylon served God's purpose. So the tannin are the opposition. They should be viewed as either actual existing spirits -- "the serpent" -- or as metaphors for the serpent, depending on how you understand the serpent in Genesis and other texts.
tannin was also the word used for snakes created by Pharaoh's magicians (and also by Aaron) in Exodus 7:9-12. They are referred to as vipers in Psalm 91.13 "you will tread on the young lion and viper [tannin]".
In Isaiah 27.1, Leviathan is declared to be one of these tannin. In Isaiah 51.9, God will kill the serpent [tannin] and in Psalm 74.4, God will crush the head of Leviathan.
Thus this is how the old testament refers to "the serpent" in a malevolent sense as the enemy of God, as opposed to a biological snake, which is nachash.
- H. Niehr, “תַּנִּין,” ed. G. Johannes Botterweck, Helmer Ringgren, and Heinz-Josef Fabry, trans. David E. Green, Theological Dictionary of the Old Testament (Grand Rapids, MI; Cambridge, U.K.: William B. Eerdmans Publishing Company, 2006), 727.