Calling AM's oki a "vortex" is way too generous, lol. It's good but it's nowhere near true vortex territory (and it's peanuts to characters like Wonder Woman and her 50/50s, or Doomsday and his 1-move oki of God).
Water Shield is also kind of a hard move to use against good opponents for anything other than a fake-out. it's kind of something to do to SUGGEST to impressionable players that you might go for silly gimmicks with it and leave yourself open to throws or whiff punishment on a dash cancel...and then the joke's on them when you never do it again, but instead respond to and/or punish the impulsive thing they did trying to bait it. I really hate when people call it a "parry" because that's not actually how it works. It's NOT something you mash under pressure because unlike a true "parry" (Batman, WW), you don't gain its benefits on the first frame, and there's not enough wakeup invincibility to just wake up with it and shit on people's oki (though I really wish I could against Doomsday DF+2). It's not useless, but it's very situational, and it's NOT godlike.
He has amazing zoning at mid range, but certainly not at long range unless your opponent is TERRIBLE (all caps) or plays a character that has extremely poor punishes or counters for DB+2. 90% of Aquaman's zoning is trying to get your opponent to either jump at d+2 range or get whiff punished/just plain hit by b+1 or b+2. If you control that range, yeah, he's pretty godlike, lol. But his projectiles are ass unless your opponent won't stop hitting stupid buttons at VERY stupid ranges. He's NOT a long-range character.
The best Aquaman is a minimalist Aquaman IMO. Don't hit any more buttons than you need to, unless your opponent is for some reason absolutely terrified of you. This is part of what makes him such a dominant character, he makes people pay DEARLY for basic footsie mistakes compared to most other characters.
tl;dr most of what you said is right, he is pretty godlike, lol...rock on Arthur