Full SPOILERS ahead for the ending of Aquaman! You’ve been warned …
Aquaman, like a tidal wave, has crashed into theaters, telling the story of Arthur Curry’s battle for the throne of Atlantis. The film’s mid-credit scene provides an ominous glimpse at what threats Arthur may be facing in the sequel. We’re going to break down what those threats are, but before we dive in, know that we’re going to be wading into spoilery waters, so consider yourself warned.
The mid-credits scene opens on a coastal shack belonging to Randall Park’s Doctor Stephen Shin, a marine biologist who appears throughout the film on TV news programs arguing that the kingdom of Atlantis actually exists because apparently, Aquaman’s fame post-Justice League wasn’t good enough to convince people. Before long, it’s revealed that Shin has a house guest: Black Manta, who we assume was rescued by Doctor Shin after being defeated by Arthur in Sicily. Manta wakes up and Doctor Shin immediately peppers him with questions about his encounters with Aquaman and Mera. The two strike a bargain – a squid pro quo if you will – for Manta to lead Shin to Atlantis in return for Shin’s help killing Aquaman.
Source: IGN.com Aquaman Post Credits Scene Explained