Mer-friends, little known fact…Superman dated a mermaid!
Lori Lemaris first appeared Superman #129 in May of 1959, she hails from Tritonis, a city in the lost continent of Atlantis. Lori’s mermaid abilities include – breathing underwater, fast swimming, telepathy, transformation (human-to-mermaid only). Lori and Clark Kent met while they were in college, where Lori was attending classes while hiding her true Mermaid identity. Being from two different worlds (literally!) their romance wasn’t meant to be, but they remained friends and Lori continues to appear in DC comics, most recently in Justice Leagues.
You can read more about Superman’s mermaid girlfriend on Wikipedia!