From the Super Mario Wiki
Blurps are green colored, goggle-wearing fish encountered in the various underwater levels of Super Mario World. Blurps, like Cheep Cheeps, will often simply swim aimlessly in one direction, injuring Mario if it collides with him. As Blurps are fairly weak, they can simply be defeated by shooting a fireball at them as Fire Mario or by bashing them with a cape as Caped Mario. They are considered cousins of Cheep Cheep (in fact, they have a similar name in Japanese - Bukubuku).
Blurp in Super Mario World and Super Mario Land 2.
Blurps make a reappearance as underwater enemies in Super Mario Land 2: 6 Golden Coins. Much like their Super Mario World counterparts, Blurps aimlessly swim in one direction and can be defeated by a Fireball. Blurps are found primarily in the Turtle Zone.
A single Blurp appeared in the Super Mario World TV series episode "Mama Luigi" where Luigi was attacked by it but he swim and stomp on it. The appearance of the Blurp is different, looking more like a Boss Bass than its game appearance. Like the Blurp, it is green in colour and has red fins, but in doesn't wear goggles and is very fierce.
Like various enemies of Super Mario World, Blurps also return in Super Princess Peach. Some of them are affected by the rage vibe of the Vibe Scepter and are called Mad Blurps. They will pursue Peach if she is in front of then.
Names in other languages
|Japanese onomatopoeia for a bubbling noise; officially romanised as "Buku Buku"