Vulcania Submarine have written an exhaustive tribute to the divers, equipment and processes that went into filming the underwater sequences during Disney's classic 20,000 Leagues Under The Sea. Fantastic.
"Filming the underwater scenes for Leagues was the greatest technical feat of its kind ever attempted. Nothing on this scale had ever been done before. The operation was so unparalleled, and the photographic methods were so revolutionary, that the United States Navy sent observers along to film the operation and see what they could learn about underwater photography from the Disney team."
"...the Disney diving systems combined hard-hat and SCUBA gear with unique art-metalwork that was out-of-this-World... The rigs were tremendously heavy: well over two hundred pounds each."