Doctor Who: 14 Cool Details Revealed In Steven Moffat's Wedding Of River Song Commentary
5. The Actors Playing The Silence Are Stood BEHIND The Water Tanks
This is one of those details that suddenly seems really obvious the moment you learn it, but somehow, you don't really register it while watching the episode.
When the Doctor arrives inside the Area 52 pyramid, he enters a small room with a bunch of water tanks embedded within the walls. Each water tank contains one of the Silence creatures (a "Silent", if you prefer) just stood there, looking all menacing.
It's a terrific visual, and these shots were staged and filmed in a really clever way.
Rather than getting them all wet, the Silence performers were instead placed behind the water tanks - with bubbles added in the foreground by the production crew - making it look like they're inside the water.
This whole idea was Moffat's: while on holiday in Dubai, he visited an aquarium that was "built into stone walls", and he found this so eerie that he imagined what it would look like with monsters stood inside the tanks. Imagine no more, Mr. Moffat.