It took these highly intelligent, seasoned pilots less than 3 minutes to destroy themselves once they lost their visual reference points.

They had good visual reference to the world outside.

In this manner, the collection serves as a permanent visual reference source.

Physical sets were constructed so the actors could have a visual reference, as opposed to using green screen technology for every scene.

Likewise, all core diving skills, including equipment function, air-sharing and other emergency protocols must be practiced until they can be performed without visual reference.