1968, at the ripe old age of 15, most Fridays after school we'd (3 teenagers) take the ferry to the north jetty in Port Aransas, Texas. We'd spend the weekend camped out there to fish for sharks. The first order of business was to "catch bait", that is, snorkel around the jetty and spear some sheepheads.
I could see the bigger and better "targets" beyond my breath-hold range, and really really wanted to go there - I was hooked.
I scrounged and saved the cash to buy some jetfins, booties, mask/snorkel, and a pole spear (still have all except the booties). Then, in 1975 upon graduation from college I scrounged and saved to do OW certification, using the same mask and fins.
My first non-instructor-led dive trip (a month after cert) was to Vortex Springs, FL, where my second dive ever was a cave/deco dive with a NACD diver I met there (guy who was supposed to be my "buddy" didn't want to dive). Talk about the ultimate trust-me dive. The NACD guy became my regular cave diving buddy, and we continued cave diving until 1990 when I gave it up.
Somehow we survived (I did both nacd and nsscds certs along the way, but real credit goes to mentoring by what are now some of the legendary names in cave diving), and now I do strictly open/warm water dives with my family, and no, they don't do it the way I did it.