I remember the once I saw them fill it (while I was working there, but not opening that day), and wow, do I wish I'd had a camera! I didn't know that it was 2x4s that made the rapids - sometimes the simplest solutions are best. I was most surprised, though, that it filled up so quickly! It just took about 5 minutes.
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PO!NT OF VIEW - A Different Look at Roller Coasters
http://www.crosswinds.net/~justmayntz/thrills/