A 'fish' is generally agreed to be 'Any member of the groups Chondrichthyes, Actinopterygii, and Sarcopterygii, aka, the Cartilaginous, Ray Finned, and Lobe Finned fishes.
However, using our good friend the cladogram, it becomes clear that this definition may include... Another group, so to speak. Its the Tetrapoda, aka, the four legged vertebrates.
This means, via cladistics, you yourself are a fish, as well as frogs, snakes, bears, dinosaurs, testudines, and anything else that walks and bears four total locomotor limbs supported by an internal body structure.
Fun Fact: All images in this blog will be as low quality as possible to save possible space.