Game Of Thrones Season 7 Premiere: 9 Things You Might've Missed In 'Dragonstone'
9. The White Walkers March
One of the reasons that line about the waves is intriguing is because of what we actually see of the White Walkers and wights in this episode. Looking back at the scene, it does appear as though the ground in front of them isn't just the snowy terrain we're used to seeing Beyond-the-Wall.
When first analysing this a bit closer, I thought it might've been grass: it does appear as though you can see patches being iced over. The implications of that would be we're seeing the future here, after the White Walkers have invaded Westeros, and are well on their way towards the living and the Great War.
Combined with the missing line, however, it adds to the possibility that what we're seeing here is the army actually walking on the frozen water, although that doesn't suggest either way if it's the past or present.