The Red Shark Gang is a group of criminals in Satan City that are lead by a man named Rock. Jimbo and Slimjim are the only two members of the gang who appear in the Dragon Ball manga, the other ones appear only in the anime.
The groups known members are named Slim Jim and Jimbo who are first seen getting chased by the police and they trick the police and make them crash. All of this is seen by Gohan who tells them that what they did was dangerous and challenges them to a fight.
Later, Rock challenges Mr. Satan to a fight after taking the Satan City Mayor hostage. Satan stays home out of fear, though his daughter, Videl, challenges the gang in his stead. She and Gohan, disguised as the Great Saiyaman, defeat the criminals and round up all the present members for the police.
Video game appearance
The Red Shark Gang appears in Dragon Ball Z: Buu's Fury, with looks different from those they have in the anime, but they still play the same role.