The Deep Ones from H. P. Lovecraft's The Shadow Over Innsmouth
The Fishmen are a race of fish-like humans from the anime One Piece. They are modeled after different aquatic lifeforms. The Fishmen can breed with Giants to create Wotans.
The Fish People from the radio broadcast Alexei Sayle and the Fish People
Frog-Man and the Ani-Men version of Frog-Man from Marvel Comics
The harbor master, from Robert W. Chambers's 1904 short story "The Harbor-Master"
The titular creatures from Humanoids from the Deep
The Hynerians from Farscape
Ichthyander from Amphibian Man by Alexander Belyayev
The Kanassans are a race of fish-like humanoids from the planet Manassas. They are said to possess psychic abilities, including being able to read minds and see into the future. They featured in the special Dragon Ball Z: Bardock - The Father of Goku
In the Dragon Ball Z series, the alien race of Sūi' (one of Frieza's foot soldiers) is a race of humanoid fish-like aliens, who worked in the Galactic Frieza Army
The TigerSharks in the cartoon series of the same name
Mr. Toad from The Wind in the Willows
The Trench in DC Comics.
The tritons from the Dungeons & Dragons role-playing game setting