How can Mera, Vulko and Atlanna breathe air while other Atlantians can't?

I am NOT an expert on Aquaman/etc., I was always a Batman & Wonder Woman nerd when it came to DC but.... if I had to venture a guess on the High Borns breathing air/water while others. Or multiples guesses.

1.Royal breeding: Many nobles being the 3rd sons/2nd daughters/etc. of the direct royal line, so they get married off to other nobles, creating these Royal Cousins as far as blood is concerned while their actual rank may be Viscount or Countess. But the royals that are direct, might not always marry within the kingdom (or species, in this case) and may marry outsiders for the purpose to trade/treaties, so a King's first born son is married to the 3rd daughter of a non-Atlantian, and their children are like Aquaman. But those children all marry Atlantians, and their children marry Atlantians, and so on. But that gene is still in there, especially if you have these Royal Cousins sometimes marrying other Royal Cousins, so they get a double-dose of this old gene.

2.Genetic manipulation, in the distant past, to make the Leadership Class able to go outside the ocean to deal with other kingdoms. So if you had the bad guys like Steppenwolf, showing up to nuke the whole planet - these people who are able to breathe air, can team up with the Amazons & co. to defeat the Big Bad before it fully invades the seas.

3.Perhaps, way back when, there were some Atlantians who had the genetic oops that allowed them to breathe air, while others did not (think that first monkey with an opposable thumb), and so it was decided because they could venture on land to make treaties or scoop up resources, that those who could breathe in both were advanced to higher positions like General and/or King, while the others were left to be the rank and file.