Did you ever watch the animated Aqua Man on TV, as a kid?
The seasons from the lates 60s and early 70s were a little before my time, so they weren't on tv, unfortunately. They look classic especially compared to some of the various iterations from the 2000s.
The poster piqued my interest for the movie. As you said, all the sea life appear to be under Aquaman's control, like he's the Lord of the seas, with Atlantis in the background, etc.