Six Flags Discovery Kingdom (SFDK) Discussion Thread in Theme Parks, Roller Coasters, & Donkeys! Posted September 5 Here is a trip report for Saturday. Sidewinder Safari experienced a delay in operation while I was in line for it. You could hear the sound of birds chirping, although I don't think there were actual birds. The ride was fun with twists and u-turns, although bumpier than I anticipated. Starting in the afternoon, the lines moved slowly. Thrilla Gorilla and The Flash: Vertical Velocity were closed.