This is surely a unique film. Although I possess only the US-version with the added scenes where 4 kids are visiting the Museum of Natural History and as they wander through the halls of giant prehistoric skeletons one of the boys stops by a "model" of a native indian and starts dreaming the very journey the original Czechian film is about.
With a boat they find by the shore of a river they journey downstream and to their astonishment they find that the wildlife on the fastland is prehistoric. The longer they travel the more ancient the animals. Its a kind of an educational kiddie movie without any melodramatic plot,but the whole business is fascinating as the kids who are trapped on the "river of evolution" must from time to time seek shelter on land. They confront a mammoth and a lurking caveman. From the Tertiarian Age they are attacked by a Diatryma bird and see a living prehistoric world exhibited in a way very unusual from other prehistoric adventures. The special effects are invented by the director himself, and works very well and the atmosphere of living prehistory is still unsurpassed, I think.
As they travel further down the river they meet dinosaurs and pterosaurs and finally they are forced to cross a Carbonian swampland infested by amphibians and insects until they reach the end or should I say, the Beginning: An endless Ocean where Life started. This plot was reprised in the british film Land That Time Forgot (`74).
A warm and educational movie (although we know more about Evolution today), I can recommend to everyone with that timegazing eye.
