This one has been bouncing around for a day or two and I think it may be a long shot, but you never know. A site called SchmoesKnows says they know how Aquaman will be introduced into the DC film universe… and that it has already happened.
The report says that the scene in Man Of Steel where Clark Kent rescues workers from a burning oil platform and is tossed into the water when the rig collapses is the key. While he is unconscious underwater we see two whales approaching and making wale sounds. They appear to be swimming toward our hero.
Looking at this story I have to say I'm extremely skeptical about it. The source on this is supposed to be someone at a dinner who overheard someone at another table who was talking about it. That may just be the definition of sketchy.
But, it does seem kind of strange that the two whales are there in the movie. I could see Zack Snyder laying the ground work for the sequel that early. I would just like to hear that from a more reliable source.