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 surface ...

For deep reef divers, descending into the ocean’s mesophotic layer can feel like exploring the moon. Discovering never-before-seen marine species is part of the mission. The deep diving team heads ...