For deep-diving mixed-gas divers, it's far worse. Routinely diving below 130 ft (40 m), the divers are always in pitch darkness, relying on work and helmet lights, and they are tethered to the ...

What's known as a "standard diving dress" — consisting of a metal helmet, a hose to supply air pumped in from the surface, a canvas diving suit, and boots — was developed in the 19th century ...