By the mid-’50s, the experience of exploring the deep in this way was still quite uncommon, but ingenious DIYers wanted in on the action. Pfister described underwater diving as “a brand-new sensation, a feeling of really being out of this world.” In 23 photographed steps, he explained how to repurpose then-ordinary items like surplus CO2 tanks, high-pressure connectors from oxygen-therapy-equipment dealers, and aluminum sheets to build an aqualung—all for about $40 (about $438 in 2022 money). Still, if you’re motivated to shoulder the potential costs and build your own dive gear from as close to scratch as possible, the parts are out there—although what was cheap and readily available in 1953, like brass pipes, may be expensive now. Besides, we must also consider advances in apparel, like the invention of buoyancy compensators—diving vests with air pockets that allow users to control their rise and descent. Such equipment makes things much easier on your spine than Pfister’s plywood plate and harness. The biggest concern, however, is safety. Underwater diving regulations have changed quite a bit since the middle of the 20th century. After two people died in California in 1952, Scripps Institution of Oceanography, which led the way in scuba’s nonmilitary adoption in the US, developed a set of rules and regulations for the activity; these include air-quality standards and specifications for breathing masks and helmets. The first edition was released in 1954. Even so, it would be difficult to make any DIY gear conform to the requirements. In the ’50s, though, Pfister was a bit optimistic as he doled out advice for diving newbies ready to take their garage aqualungs out for a plunge. “Using a diving lung,” he wrote, “is as safe as crossing a street.” He cautioned, however, that even crossing a street has its rules. “You, for the first time, are about to cross into a new medium—deep water.” This story originally ran in the Fall 2022 Daredevil Issue of PopSci. Read more PopSci+ stories.