There's a difference between technical work and being tech support. Usually, the latter are the ones not good enough to be systems administrators. Higher tier tech support comes close, but nearly every tech support person I've met was some drone who read solution recipes out of a book.
Submarine crews are usually very intelligent and highly skilled at their job. They can't count on outside support and have to be able to operate autonomously for weeks or months on end. When sub sailors get out of the Navy, they're usually able to find suitable employment quickly and have the mental tools to do nearly anything they like.
I was a Sonar Technician (STS1(SS)) on two 688 class attack subs for 6 years and stayed in the ASW world for a few years after getting out of the Navy, then shifted into systems engineering and Unix administration. I'm now a systems architect running large-ish distributed computational clusters. I know of guys who became electrical engineers, doctors, teachers, etc.