It was a submarine slightly larger than a boat. Light red paint, or perhaps rust, covered the exterior.
Only one room existed in the submarine, the control room. There was enough room for a grill, the controls, and a serving window.
This establishment consisted of two employees:
Patrick Star - He works as a cook.
SpongeBob SquarePants - He drives the mobile restaurant despite not having a license and not being able to drive well.
Role in series
Before the episode occurred, this somewhat primitive submarine was used by an unknown animal, most likely a human. Somehow, it sunk and became useless to control.
Later, SpongeBob and Patrick found its periscope sticking out of the ground, dug it, and took possession of it. At the Krusty Krab, Mr. Krabs had the idea of "bringing the Krusty Krab to the customers." He did so by converting the submarine into a mobile restaurant. While SpongeBob and Patrick were trying to sell Krabby Patties, Plankton attempted to use his own traveling restaurant. The duo had some unusual ways of selling the Krabby Patties; they paid the customers to eat and made a deal to get the customers to eat burnt patties (rocks). They accidentally fall into an abyss, but they unexpectedly sold Krabby Patties and chum-wiches from Plankton's restaurant to a monster. The monster went chasing Plankton as he thought Plankton was dessert. SpongeBob attempted to get out of the abyss, but left behind the heavy money, much to Mr. Krabs' surprise and horror. They managed to bring back several tons of colored rocks, however.
SpongeBob and Patrick's roles are somewhat reversed in this episode since SpongeBob's a good cook even though he's driving; and Patrick's a good driver even though he's cooking.