NHK Twinscam

The NHK Twinscam is a digital-optical-mechanical video camera system designed by the Japanese broadcaster NHK for covering aquatic sports events. It uses digital image processing technology to combine video from two synchronized motion-controlled cameras, one above water and one underwater, in real time, to create the illusion of a view from a single camera that can look through air and water at once as if they had the same refractive index.^[1]

It was used at the 2012 London Olympics to televise the synchronized swimming events. It has been used for the same purpose in Japan since 2010.^[2]