Comics
Fishboy is an Atlantean, and a friend of the Tick. He is a fish based superhero, and he can telepathically communicate with seas creatures, but he can’t swim, because he was raised in Montana.
In other media
In the 90’s cartoon he meets the Tick for the first time at the Comet Club, a night club for superheroes. He shows up, again to help the Tick ad his allies stop an evil ant army.
In the first live-action show, he is portrayed as a sidekick to the superhero, the Angler, who makes fun of Fishboy’s webs.
While Fishboy himself doesn’t appear in the Amazon show, an Atlantean character did. A humanoid lobster called Lobstercules by the public. She claims that she was a warrior who served the Atlantean royal family.