Why is the Cosmic Egg said to Float on Water?

 

The cosmic egg of the ancient esoteric literature is often described as floating in the waters. The bronchial tree touches the realm of the waters (oxygenated blood) only at the level of the alveoli so why is it then that the entire egg (bronchial tree) is said to rest upon the waters? One reason might be that the "waters" in this case refer not to the flow of oxygenated blood in the pulmonary veins but to the pulmonary arterial flow. Normally the arterial flow is, by virtue of being the "poisonous" flow, referred to in the lower reaches of the bronchial tree as "fire" and only after being transformed by the "milk" pouring forth from the udders (alveoli) of the cow-like respiratory bronchioles does it assume the form of water. But there can surely be some flexibility in definition and it could be that in the passages relating to the cosmic egg, it is the arterial flow that is referred to as the waters.