Deep-sea diving is a highly complex and dangerous endeavor. It also has great rewards - treasure and salvage from shipwrecks, military and industrial applications - so reaching for the depths has been a pursuit for inventors for centuries.
In 1715, British inventor John Lethbridge designed a diving suit capable of reaching depths of 60 feet and staying for more than 30 minutes. Here's an article about vintage diving suits.
(via Everlasting Blort)