* New discoveries: Scientists are constantly discovering new species.
* Classification: The way we classify fish can change, and new genetic analyses can lead to reclassifications.
* Deep sea mysteries: A huge percentage of the ocean remains unexplored, so there are likely many undiscovered species.
However, we can give you a rough estimate. Scientists believe there are around 30,000 to 35,000 known species of fish.
Keep in mind that this is just an estimate, and the real number is likely much higher. The ocean is a vast and mysterious place, and there's still so much we don't know about the creatures that live there.