Another close friend of SpongeBob is Sandy Cheeks, a squirrel from Texas. She is a scientist and an expert in karate. She lives in an oak tree entrapped in a clear glass dome locked by an airtight, hand-turned seal. When outside of her dwelling, she wears an astronaut-like suit because she cannot breathe underwater. Mr. Krabs, a miserly crab obsessed with money, is the owner of the Krusty Krab restaurant and SpongeBob's boss. Krabs has a teenage whale daughter named Pearl, whom he values equally with his riches. His rival, Plankton, is a small green copepod who owns a low-rank fast-food restaurant called the Chum Bucket, located across the street from the Krusty Krab. Plankton spends most of his time planning to steal the secret recipe for Mr. Krabs's popular Krabby Patty burgers, so as to gain the upper hand and put the Krusty Krab out of business. The majority of Plankton's plans come from his intelligent yet sarcastic computer wife Karen, who is more competent and less conceited than him. When SpongeBob is not working at the Krusty Krab, he can often be found at Mrs. Puff's boating school (the underwater equivalent of a driver's education course). SpongeBob is perpetually unable to pass Mrs. Puff's exams, which is why he almost always walks around town.