Job 41:31 - Matthew Poole's English Annotations on the Holy Bible

The deep; the deep waters, or the sea, which is called the deep, Psalms 107:24 Jonah 2:3, as it is explained in the next clause. To boil like a pot; to swell, and foam, and froth by his strong and vehement motion, as any liquor doth when it is boiled in a pot. The sea; either the great sea, the proper place of the whale, Psalms 104:25; or the great river Nilus, which is called a sea, both in Scripture, as Isaiah 11:15, and in other authors, (of which see my Latin Synopsis,) as Euphrates is called the sea of Babylon, Isaiah 21:1 Jeremiah 51:36; or lakes or pools, which are most frequently called seas, both in the Old and New Testament, as every one knows. And in such lakes the crocodiles are no less than in Nilus, as it is attested by Herodotus, and Strabo, and others. Like a pot of ointment: this clause seems to be added very emphatically, to intimate that this leviathan causeth not only a vehement commotion, but also a great fragrancy in the sea or waters where it is; which, though it was not observed by the ancients, yet is unanimously affirmed by later authors upon their own knowledge and experience, that it casts a perfume like musk; of which see the names and words of the authors in my Latin Synopsis.