Scenes like this one are rendering for eternity. Even with low quality and resolution. I think cheaper and faster would be catching a train, go to the sea and shoot this scene with a cellphone. But... I don't have inflatable G-baloon, sadly.
I'm really looking forward to a new engine in Blender Eevee, with a hope it'll make a significant difference in rendering times. Of course, if Eevee will be stable enough :)
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