Your right stamina. Marvel characters tend to have longer stamina then dc characters most of the time.
Thor has been seen to fight Zeus in a stalemate for months striaght with out getting tired. He has also done the same with hercules but that time was weeks, and it was only hand to hand.
Superman could barely hold out on doomsday for a few hours....
In Stamina Namor may take it. I've never seen Aquaman get tired I've only seen him come back at the last moment like how he beat Zoom.
Orion can battle unending like that. So can highfather and Darksied. Also, Zeus was taking it pretty easy on thor. When Superman fought DD the first time, he'd been depowered and fighting someone who was his superior who meant to kill him.
Aquaman he has by far the best speed feats and he has already swam at least half the globe without stopping in an old Wonder Woman issue.
Plus I have never seen him get tired but I've seen him fight for days in some Aquaman and JLA issues.
In the latest issue of Nightwing a scientist also makes mention of his endurance saying he couldn't achieve these levels through science.
So even if stamina comes into play Aquaman has this one easy.