April 1999
The oldest certification I hold is not on the credentials page of this site. It is a PADI Open Water card, issued on 25 April 1999 by a dive shop in Moema, here in São Paulo. It predates my first CCNA by about a year.
The credentials page is careful work. Every entry has an issuer, most have dates, many have a verification link, and a build check makes sure none of them claims something the evidence does not support. That care is the point of it: someone deciding whether to put me in front of their engineers should be able to check.
But a page built to answer one question answers only that question. It is an argument about competence in a specific domain, deliberately narrow, and everything outside the domain is invisible on it by design. That is correct, and it is also worth saying out loud occasionally, because a person is not their filterable attributes and a career is not the list of things a database can verify about it.
What diving and change windows have in common
Here is the part that is not sentimental.
Recreational diving is a discipline built almost entirely out of decisions made before you are in a position to need them. You plan the dive and dive the plan. You agree a turn pressure — the point at which you go back regardless of how interesting it has become — before you get in the water. You check your buddy's gear and they check yours, on the surface, where checking is easy. You know your maximum depth and your ascent rate in advance, because the moment you need those numbers is exactly the moment you will be least equipped to work them out.
Every one of those is in the five practices that this site argues the failure cases demand: a baseline taken before you need it, a rollback agreed while everyone is calm, a limit set in advance and honoured when it is inconvenient, a check performed by a second person, a boundary that does not depend on things going well.
I did not learn that from diving and then apply it to networks. I learned both at roughly the same time, in my early twenties, and it took me another two decades to notice they were the same idea. The people who taught me to plan a dive and the people who taught me not to touch a production firewall on a Friday afternoon were making the same argument about the same kind of risk, and neither of them mentioned the other.
Why it stays off the page
Because the credentials page has a job and this is not it. Putting an Open Water card between an F5 solution-expert certification and a Fortinet track would not make the page warmer, it would make it less useful, and the person checking whether I can teach their team about web application firewalls would have to read past it.
So the card lives here instead, in a post, where the context can be explained rather than implied by a row in a table.
And the reason I am mentioning it at all is the one I gave when I first put the card online, which I still think is the best advice in this entire site: get out there and play. Almost everything I know that turned out to matter, I learned while doing something that was not obviously my job — on the radio bands as a child, on bulletin boards as a teenager, underwater at twenty-three. None of it was strategic. Some of it turned out to be the whole foundation.
The certifications on that page are real and I worked for every one. But if you are early in this and reading the list wondering how to build one like it, the honest answer is that the list is the residue and not the method. The method was curiosity that did not check first whether it would pay.