here's a quote from one of my ebooks on the subject
Keep in mind, that the ancient past has been foraged from for millenia, to uphold various religious or non-religious positions, which by necessity,
requires some descriptions be virtually ignored, while favoring others. But let's see what happens when all the descriptions are applied and the
symbols are re-interpreted as an integrated whole. To achieve this with the ABZU references, we also need to incorporate related, associated symbols.
One such association is the dragon or "Tiamat."
Tiamat also had the distinction of several different descriptions that seem totally unrelated. In the ancient texts it was referred to as a dragon, a
monster, the salt water ocean or sea, the water of chaos, a goddess of birth, a constellation, and the gods and sons of god, also emerged from it. 
Some pick only the dragon definition to elaborate on, while others choose the water of chaos, the ocean salt water, or the birth goddess. And still
others, assume Tiamat and Abzu are one in the same. And, they are all correct! Each of those definitions do indeed fit Tiamat, although it isn't the
"Abzu" (or vice-a-versa), specifically, it does merge with the Abzu and even says as much in the ancient texts. Allow me to explain:
You see, the ABZU was an entrance to another place or many other places. It was a subterranean gate, apparently filled with swirling water, like a
whirlpool. In the following excerpts, notice the gate is a conduit betwen the earth and heaven. Some believe that it simply meant the top of the
Ziggurat was heaven and the bottom of the Ziggurat was the earth, but that doesn't fit with the rest of the information, especially the references to
the gate connecting the "holy shrine" in the depths of the "sea" (a misunderstanding of "ABZU", which was also known as the "abyss") and the
Your great house is founded in the Abzu, the great mooring-post of heaven and earth. [...]
The lord established a shrine, a holy shrine, whose interior is elaborately constructed. He established a shrine in the sea, a holy shrine, whose
interior is elaborately constructed. The shrine, whose interior is a tangled thread, is beyond understanding. The shrine's emplacement is situated by
the constellation the Field, the holy upper shrine's emplacement faces towards the Chariot constellation. (emphasis, mine) 
It was a doorway of sorts, a gate to the "netherworld" which was in reality, a gate to outerspace, and it had at least one exit somewhere by the
constellation "The Field" (possibly a reference to the Great Square of Pegasus, more on that later). It was the access point to Enki's meeting
chamber and at least one of his very special throne rooms.
However, every entrance or exit, needs a hallway in order to get from point A to point B, and that's where Tiamat comes in. Tiamat is the pathway
through the hourglass. It embodies the application of "As above, so below," the figure eight ouroboros and the infinity loop. In short, Tiamat was a
wormhole connected to the ABZU, which was the gate of the wormhole. The two "waters", salt and sweet, merged at the gate, creating a swirling
vortex, the watery chaos of Tiamat.
And I quote:
Your door is a lion who [seizes a man] [...]
With such a connection to the Earth, the gods and sons of god, could literally emerge from the ABZU, be "born" from it. It would appear as if the
ABZU were giving birth from the birth canal of Tiamat's swirling waters. These are the "primeval" waters from which the prototype, primeval mound
(Enki's E.ABZU), arose. This is also the origin of the belief that an interdimensional gate is opened via sex magic: The ziggurat or pyramid (and
later, the obelisk and benben) representing a phallic symbol and the Gate and Tiamat, representing the vaginal opening and birth canal.
So, let's review what we know about Tiamat, so far:
1. Tiamat as a dragon, referencing that it's a wormhole, an ouroboros pathway.
2. Tiamat as "salt water ocean" merging with the freshwater ABZU, the two waters combining in a swirling whirlpool at the ABZU gate entrance.
3. Tiamat as the water of chaos, referencing the whirlpool formed at the ABZU gate connection to the wormhole.
4. Tiamat as a goddess of birth, referencing the emerging of the "gods" from the wormhole through the ABZU gate.
5. Tiamat as a constellation, referencing the wormhole connection to a place near the "Field Constellation."