Wiley and Grampa set out for some fun in the sun at Gingham County 's finest water park, Castle Waterhösen. But when robot sharks and half human, half crawdad creatures attack and Nate Farkles goes missing, Wiley and Grampa must abandon dreams of conquering the mile-high slide and discover what masked phantom lurks in the bowels of the park. Will Wiley and his posse become fish food or will the crawdads be tossed into the boiling crockpot of justice? Get ready for a wild ride down Mount Flushmore !