Hart primarily designed his system to help sailors and boat owners who found themselves in an emergency situation where they needed to repair their boat in a remote location. For instance, to free a fouled prop.
In a nutshell, this patented handheld device uses compressed gas to produce perfect air rings. The idea is that you simply 'tag' your buddy with these air rings to attract their attention in low visibility.
I am sure that we have all told a positively blue child who is shaking like a leaf “that now is a good time to climb out of the water and get dry”. And to hear the emphatic response through chattering teeth, “but I’m not cold”!