Selma star David Oyelowo is getting as much sleep as possible ahead of his directorial debut, because he fears he’ll be exhausted as a first-time filmmaker.

The actor is stepping behind the camera for The Water Man, which starts shooting in May (19), and as excited as he is about the prospect of calling the shots on set, he knows he won’t be getting a lot of sleep.

“It's been something I've been wanting to do for a while and I'm very glad it's finally coming to fruition,” he says. “I've directed plays and short films and I love the process of just telling stories and doing that in a very total way as a producer, actor and director.

"I really relish the prospect of it all but I'm sure I'm going to be more tired than I've ever been in my life!"

The actor-turned-director's debut revolves around a 10-year-old boy on the hunt for a mythical figure, The Water Man, who he believes can save his mother from cancer.

The film will shoot in Portland, Oregon over the summer.

As well as directing the film, David will also star and produce alongside Selma co-star Oprah Winfrey.

Oyelowo previously stepped behind the camera for the short film Big Guy in 2009. The project featured Josh Gad and Charlie Cox.

Meanwhile, the star's upcoming acting credits include Come Away, Chaos Walking and TV mini-series Les Miserables, in which he plays Javert, the role Russell Crowe tackled in Tom Hooper's 2012 movie musical adaptation of Victor Hugo's classic tale.