A.T. Robertson Commentary Revelation 12:15

"And the serpent cast out of his mouth after the woman water as a river, that he might cause her to be carried away by the stream." — Revelation 12:15 (ASV)

Water as a flood (υδωρ ως ποταμον). "Water as a river," accusative case after εβαλεν (cast). The serpent could not follow the woman or stop her flight and so sought to drown her.

That he might cause her to be carried away by the stream (ινα αυτην ποταμοφορητον ποιηση). Purpose clause with ινα and the first aorist active subjunctive of ποιεω. For this use of ποιεω see 17:16. This compound verbal ποταμοφορητον in the predicate accusative (ποταμος, river, φορητον from φορεω, to bear) was not coined by John, but occurs in a papyrus of B.C. 110 and in several others after N.T. times. It means simply "carried away by the river."