I remember watching Land of the Lost on saturday mornings as a kid and totally being ok with the special effects. I didn't even think of special effects, I just saw a poor scared family's raft fall down a terrible rapids and waterfall. It all looked plausible and real enough. When I saw this again recently I was stunned at my then willing suspension of disbelief.
Check it out...
***Update***
Bear just watched this and said, "That looks fake. That TOTALLY looks fake." So he noticed.