I have not been on the Jurassic Park ride, but we wore ponchos when riding Dudley Dooright and Bluto's Barges. In Dudley Dooright, they kept us pretty dry. In Bluto, the water came down on us so hard that it flooded the seats and came up and soaked our butts even though we had ponchos on! We tried those stupid drying machines for $5 (waste of money/time), and ended up going back to the hotel for a bit to dry off