She is a light green fish with black eyes and white hair. She wears a brown rag for shorts.
She met SpongeBob and Patrick when they arrived in the cave to play Hide and Seek. SpongeBob said, "I like it in here. It's roomy." Then the Cave Fish laughed. SpongeBob and Patrick thought the laugh came from some mice, but they were wrong. The Cave Fish jumped out and told them she had been there for forty years. She also said they would all be in the cave forever. The Cave Fish turned SpongeBob and Patrick against each other by telling them the only way to survive was to eat what you could. She said, "Eat or be eaten."
At the end of the episode, Sandy revealed herself as the Cave Fish. She gave SpongeBob and Patrick medals to show that they were survivalists. However, the duo, still in a state of hunger, almost ate her.