A.T. Robertson Commentary John 6:18

"And the sea was rising by reason of a great wind that blew." — John 6:18 (ASV)

And the sea was rising (η τε θαλασσα διεγειρετο). Imperfect (without augment) passive of διεγειρω, late compound to wake up thoroughly, to arouse.

By reason of a great wind that blew (ανεμου μεγαλου πνεοντος). Genitive absolute with present active participle of πνεω, to blow, "a great wind blowing."