Book of Enoch (1 Enoch) 60:7
And on that day were two monsters parted, a female monster named Leviathan, to dwell in the abysses of the ocean over the fountains of the waters.
Background and history of Book of Enoch (1 Enoch), and issues with this book.
R. H. Charles, The Book of Enoch (London: SPCK, 1917), public domain. The verse text is the English Wikisource transcription of that translation. Charles’s editorial signs are kept. He rearranges some verses in chapters 5, 39, 90, 91, and 106, so those chapters are not a straight 1, 2, 3 sequence.