Batman: The Brave and the Bold (2008)

S01E03 Evil Under the Sea!

Batman delves into unusual seismic disturbances and decides to consult Aquaman. Unbeknownst to the underwater hero, his brother Orm is secretly plotting with Black Manta to seize control of Atlantis. As tensions rise, the duo's sinister plans threaten the oceanic kingdom, prompting Batman to uncover the truth before it's too late.