The Copper Helmet That Built the Underwater World
Wiki Deep dive into Standard diving dress
Standard diving dress—the iconic copper helmet and canvas suit—dominated deep-sea work for over a century, enabling salvage, civil engineering, and pearl diving. Invented by the Deane brothers and perfected by Augustus Siebe, it could reach 600 feet and weighed up to 190 pounds. This Wikipedia deep dive traces its evolution from 1820s smoke helmets to helium rebreathers, and explains why it was finally superseded by lighter gear.
The real success of the equipment was a valve in the helmet that meant that it could not flood no matter how the diver moved.