Was recently reminiscing about Manteca Waterslides and came across this forum, wanted to add a little extra info:
The river rapids would split into 2 paths, the left path had a rather steep waterfall that would knock riders off of their tubes. I remember this part in particular since the lifeguard would always get angry at me for taking too long to get back on my tube. The right path was a slower path with 2-3 whirlpools that were a great way to extend your ride. Both paths eventually merged again just before the final somewhat steep slide down to an exit pool. I would always fall off here too and get trapped underwater a few seconds by the rushing water.
I recall there was a battle tank attraction to the right of Rampage. Not sure if it was only there for 1 year or not. Basically the tanks were fiberglass bodies on a driveable platform. One person got to be the driver and the other operated the turret which fired rubber squash balls. The tanks had targets on them and if you hit a target it disabled that part of the tank (turret/engine).
Sorry I don't have any photos, never thought to bring a camera to a waterpark. I went here 3-4 times in the early 90's and would stay at the campground and spend the day on the slides. Rampage was always my favorite, especially the cute girls that always wanted to race!