Chronicles of Jerahmeel, by M. Gaster , at sacred-texts.com
V. On the fifth day He brought forth from the waters all manner of winged birds, male and female, all manner of locusts, and also the Leviathan, a serpent which holds all the dwellers of the lower waters between his two fins. The centre of the earth rests upon the huge serpents, which form food for the Leviathan. Every day he opens his mouth, and a huge serpent comes every day to feed him. It flies and flutters and enters the mouth of Leviathan, while God sports with it, as it is said, 'Thou hast created this Leviathan to sport with it.'