Aquaman appeared at the end of the Batgirl sub-comic in Dark Knight III: The Master Race #4, the first time (to my knowledge) that Frank Miller has ever written or drawn the Sea King in any DC comic.
We catch up with Batgirl, who is simply amazed at the undersea world that is Aquaman's kingdom:
Superman bursts free from the slab--which is, I think, a portal to another dimension--and now it's time for a team-up!
I'm not following this comic, so I really don't know what's going on. Doesn't matter, really, because I sure do love Aquaman as presented here by artists Andy Kubert and Klaus Janson! The two-page spread (click to embiggen) is gorgeous, majestic, a really great Aquaman image. Get rid of those smaller panels and you've got yourself a poster!