It's air-gapped from the Internet.

The term “air gap” does not directly imply anything to do with the Internet (doesn’t exclude it, but it applies more generally than specific networks). Yes, IC uses it to signify high/low networks, but the original usage of the term was to indicate a machine with no direct connection to the outside world. The theory being (since proven wrong), you can’t exfiltrate data remotely from a device not connected to a network.

What if it’s submerged in coolant?

JWICS/SIPR/NSAnet/etc. are air gapped in that terminals are not allowed to be dual homed to any other network or to each other.

Yes, I know the inteligence community uses this definition of air gap to signify the barrier between high/low networks, but I kinda feel it misses the point of the term. If it is networked to the outside world, even securely, I feel it kinda misses the point of the “air gap” connotation (aka requiring a “sneaker net” to get data in / out). I’m likely being pedantic though, so I upvoted you as you at least gave a good response unlike others.