'Mud Slide' is set up like a baseball game. The contestant starts at first base.
The ball is pitched, purposely missed by the batter, and caught by the catcher. As soon as the catcher has the ball, the contestant has to run to second base.
Between the first and second base is a pit of thick mud that the contestant has to run, or slide, through. If they reach the second base before the fielder touches it with the ball, they win the game. However, if they're too slow, or get caught in the mud, and don't reach second base before the ball, they're forced out and the contestant loses.