The "Selma" star steps behind the camera for the new project, about a boy who embarks on a quest to find the mythical title character of the film when his mother falls ill with cancer, and he sent the finished movie to Spielberg in the hopes of impressing the Hollywood icon behind his childhood favourite, "E.T. the Extra-Terrestrial".
However, Oyelowo, who also portrays the kid's dad, didn't expect the director to be so full of praise for his work.
"I managed to get my film to him. He watched The Water Man and wrote back to me, and said, 'You're a fine director and a really good storyteller,' " he recalled on America's "The Drew Barrymore Show" as he shared the story with the child star of "E.T."
"I was just like, 'Oh, my goodness! Life is so weird!' "
Winning Spielberg's approval was a big bonus for Oyelowo, who was already feeling blessed to have another Hollywood mogul on board as an executive producer in Oprah Winfrey, his co-star in "The Butler" and "Selma", which she also produced.
"My relationship with her began with us playing mother and son (in The Butler), and that relationship sort of bled beyond being in front of the camera," he explained.
"She just continued to be a sort of mother figure in my life, a great source of advice for me, advocacy for me, encouragement for me. We share a sensibility and she's just been one of my life's greatest blessings..."
"And then in terms of The Water Man, it was something... I told her I was passionate about, and she said, 'Look, I'm gonna do everything I can to help you realise this dream.' "