i. Leviathan Rising

For what it's worth, here's the text from Job 40:15-23

Behold now the behemoth that I have made with you; he eats grass like cattle.

Behold now his strength is in his loins and his power is in the navel of his belly.

His tail hardens like a cedar; the sinews of his testicles are knit together.

His limbs are as strong as copper, his bones as a load of iron.

His is the first of God's ways; [only] his Maker can draw His sword [against him].

For the mountains bear food for him, and all the beasts of the field play there.

Does he lie under the shadows, in the covert of the reeds and the swamp?

Do the shadows cover him as his shadow? Do the willows of the brook surround him?

Behold, he plunders the river, and [he] does not harden; he trusts that he will draw the Jordan into his mouth.

Comments:

The animal's male. It's a low-browsing grass eating herbivore. It's being likened to cattle. The word "bakaar" literally means oxes. Man can 'behold' it, so it's extant and not mythical in nature. It's been created alongside mankind.

"his strength is in his loins" refers to the testicles. So unlike the ox, this animal is not castrated by men, and so it lives in the wild.

It has a navel. This is like Song 7:3: "Your navel is [like] a round basin, where no mixed wine is lacking; your belly is [like] a stack of wheat, fenced in with roses." The word for navel there literally refers to the umbilical cord in both verses.

"his tail hardens" uses the verb yah-pos, which has several applications. If used to refer to people's feelings, it means "to desire". It's like moving from one point to another point in a straight line. You desire someone's affection, and this desire is not uncertain, so it's a clear movement. This is important, because many people translate it to mean "swaying", but this implies uncertainty and a back-and-forth motion. For example, in 1 Samuel 2:25 it reads: "..for the LORD desired to put them to death." The verb is the same, and it's a clear desire: no doubt implied. Swaying would mean that the intention isn't clear. So when applied to the behemoth's tail, it too means that the tail moves from one point up to another point: it becomes erect and hard.

Compare this to verse 23: "he plunders the river, and [he] does not harden". Most translations render this as him remaining secure or unafraid (as the Jordan river surges around him), but the Jewish commentaries mention that this means that his belly does not harden from his drinking, and they compare it to the hardening of the tail in 17. It means that his thirst is insatiable. The syntax necessitates the following interpretation:

The animal is confident that it can drink the Jordan river, and it does not mean that it remains secure though the Jordan river surges in its mouth. Most translations for some reason omit the verb for hardening, which is the same as in verse 17. So its belly doesn't become full (i.e. hard), even though it plunders the river. I find it peculiar how so many translators get this completely wrong. To me, this shows biases: they think it's about a huge animal standing in a surging river, but the text isn't saying that. Nothing here is actually describing the animal's size.

"his tail hardens like a cedar" then means that the tail becomes as hard as wood. Similarly, in the language of the Sages: דַחַפִּיזָא כִּי אוּפְתָּא (Hullin 47b); hard as wood.

"his bones as a load of iron" means that if you had to carry the animal's bones, it would be like having been burdened with carrying loads of iron. So that's weight, not size.

"[only] his Maker can draw His sword [against him]" does not mean that man cannot kill the creature, but it refers to the future feast, prepared for the righteous, and God Himself will slaughter this particular behemoth.

"the mountains bear food for him" refers to Psalms 50:9-10: "I will not take from your household a bull, from your pens any goats. For all the beasts of the forest are Mine, the behemoth of the thousand mountains."

This means that all creatures are rightfully His, and so when God takes an animal that man owns, as a sacrifice, then He didn't take anything from them that wasn't already His by right. Here's the commentary of Rashi on this verse:

"That is the bull destined for the future feast [of the righteous], which grazes on a thousand mountains daily, and every day they grow back. Others explain this to mean one thousand mountains or one thousand parasangs (i.e., one mountain that is 1,000 parasangs long, or perhaps it should read: 1,000 bulls. The plural “mountains” indicates that there were many mountains of that type. [Shem Ephraim]) Others explain that this is like (Deut. 7:13): “the litter of your cattle.” i.e., mountains full of cattle, because he says, “I will not take from your household a bull.” - end quote.

So as you can see, there is no discussion about the identity of the beast. There's more discussion about the meaning of a "thousand mountains". I believe that suffices in proving that the behemoth is indeed a wild bull or some kind of water buffalo. It's not mythical, it's no cryptid, it's not a Sauropod dinosaur, nor is it some unknown giant monster. People just like to believe it's one of those things, whereas the reality is that it's a bull. I do apologize for the long comment, and I have to add that I'm neither Jewish nor Christian; I just think we should read and interpret ancient (Hebrew) literature properly and realistically. Have a nice day!