I've seen just Aquaman trailers. I saw that this is the first time Arthur Curry came to Atlantis. Arthur and Mera first met too.
In Justice League, Arthur came to Atlantis like he knew it before to borrow armors and weapons. He used the trident in battles against Superman and Steppenwolf. He and Mera seem like they knew each others before.
So, Aquaman (2018) and Justice League (2017), which happened first?