Grab a cue
From A KoL Wiki

In front of the stairway to the next level stands a shark. Next to the shark stands a pool table. "Before I'm gonna let you through this room," says the shark, "you're gonna have to sink the 8 Ball. But you gotta do it off of 30 rails, or it doesn't count."
Using considerable English and considerabler finesse, you carom the cue off of 30 rails and sink the 8 Ball.
"Impressive. Be my guest," says the shark, as he points a fin at the stairs.
Occurs in Fernswarthy's Basement.