Sure. We all know that when Aquaman is underwater, he becomes exponentially more powerful. The longer that Aquaman remains underwater, it’s akin to a sun-dip for Superman. If Superman was amped enough to withstand an explosion equivalent to the Big Bang after spending 15 minutes in the sun, just imagine what Aquaman can do after 15 minutes underwater!

That’s no ordinary suck-punch, it’s a water-dipped sucker punch! Two-fisted! Then Aquaman would drown Superman with his magic water!

Awesome! Superman wouldn’t stand a chance. . .

We interrupt this fanboy rant to return you to the rightful writer, Li Hei Bao.

Hey! I’m really sorry about that. Some crazed Aqua-Fan got a hold of my answer; they are a very spirited lot. So Aquaman and Superman underwater????

Superman creates “miles deep whirlpool” to decimate an Atlantean castle, specifically protected against him by magic.

Superman vs the Kraken. . .at least Arion in Kraken form. He fights both physically and mentally, here. Oh, and underwater.

In space, land, sea, and air, Superman remains, well, Superman. Aquaman wouldn’t have any better advantage under the briny waves.

Could Aquaman win? Anything is possible, but the likelihood is that he won’t. The best showing Aquaman ever had against Superman was in Aquaman #6:

And he had Mera’s help. Aquaman and Mera are double-teaming Superman, and he just takes the hits. No freeze breath, super-speed, heat vision, or any of his other abilities, Superman just trades punches with the both of them and keeps trying to reason with Aquaman the entire time. Aquaman gets in some great shots as well:

The result, Superman gives him an ultimatum:

Some readers tout this as a great showing for Aquaman, but it’s sucker punches and double-teaming, against Superman, who, quite frankly, isn’t even trying. Worst of all, Superman at this time was only at “half” strength, until the events of “Superman Reborn” merged Post-Crisis and New Superman together:

Source : Quora