its not a extra large hippo
if you read what is said about him its way larger then a hippo
Job 40:15 Behold now behemoth, which I made with thee; he eats grass as an ox.
Job 40:16 Lo now, his strength is in his loins, and his force is in the navel of his belly.
Job 40:17 He moves his tail like a cedar: the sinews of his stones are wrapped together.
Job 40:18 His bones are as strong pieces of brass; his bones are like bars of iron.
Job 40:19 He is the chief of the ways of God: he that made him can make his sword to approach unto him.
Job 40:20 Surely the mountains bring him forth food, where all the beasts of the field play.
Job 40:21 He lies under the shady trees, in the covert of the reed, and fens.
Job 40:22 The shady trees cover him with their shadow; the willows of the brook compass him about.
Job 40:23 Behold, he drinks up a river, and hastes not: he trusts that he can draw up Jordan into his mouth.
Job 40:24 He takes it with his eyes: his nose pierces through snares.
the hippos bones are not like bars of iron.
leviathan in job chapter 41 is a huge sea creature not a whale