The Mermerang has just one appearance, in the Episode: Shuffleboarding. It is the same as a boomerang. It is one of Mermaid Man's things to defeat evil. SpongeBob accidentaly hurts Mermaid Man and Barnacle Boy and then they had to go to the Hospital.
The Mermerang is red and has scales on it, like the costume from Mermaid Man. It is like a normal Boomerang.