- Atlantis' warrior king and Protector of the Oceans vs Ultimate Marvel's Super Soldier and biggest badass
- Aquaman is Post-Crisis Orin/Arthur Curry with all of his showings prior to Obsidian Age (when writers started to make ridiculous continuity mistakes and ignoring previously established feats).
- Captain America is Steve Rogers of the Ultimate Universe. He is allowed all of his showings up until (and including) Ultimate Comics: Captain America in 2011 (this is mainly for fairness reasons, so that Cap doesn't get much more feats than Aquaman).
- Aquaman is wearing his 90's outfit and has the Golden Hook replacing his lost left-hand (see picture, no more gear)
- Captain America is wearing his original Ultimates uniform with the matching gear and his Shield (see picture, plus shield)
- Both fighters are in-character
- No previous knowledge
- Win by any means (in-character, as said before)
A few clarifications:
Just some things I'd like to establish right away before people might make wrong assumptions about the battle:
- Aquaman doesn't use telepathy as his go-to move when he is in-character, so don't assume he will just end the fight with it right away
- Ultimate Cap's shield was not made of adamantium, that seems to be a myth. Even the official Handbook only described the shield as being made of an unnamed material
- Aquaman's Golden Hook was never damaged (only the chord) and pierced through pretty much everything Arthur tried to pierce, so it should match Cap's shield pretty well