(5 mins) This clip is from "The Making of" episode from Robert Winston's "The Human Body" BBC Series from early 1998.
It covers "The Diving Reflex", present in all babies up to about six months old. It was in the third episode of the series, but here it is as seen in the "Making Of" episode.
The diving reflex is the ability to calmly swim short distances with their bodies submerged, and almost always keeping their eyes open.
We see also how they made the sequence, and rudimentary 1998 special effects, including early use of the blue (not green) screen.
