As you can see from the thumbnails above, penciler Ivan Reis tried putting a couple different heroes in the lead position, finally settling on Aquaman (yay!). Once that was established, he moved onto a tighter pencil version, followed by Joe Prado's inks, then Rod Reis' colors, ending with the cover you all saw on the newsstands (or would have, if this was 1976). It goes without saying, awesome stuff all around!
By the way, Reis and Prado are currently selling the original art to this issue over on their ComicArtFans page, where you can also commission Joe to a custom piece! Having seen and held Reis and Prado originals in my hand, I can tell from personal experience that as good as their work looks here, it looks even better in person!