It doesn't make sense to give this film a bad rating - but it really doesn't make sense to rate it at all.
Don't assume that means that this film is so ridiculous, it's beyond redemption... well, it IS ridiculous and beyond redemption; but it is certainly enjoyable on its own terms.
If this film is easy to misunderstand, it's because it's really difficult to say what 'it's own terms' really are. It begins clearly intending to compete with the successful Godzilla series; but somewhere about mid-way, it suddenly decides to be about a lonely young boy. In order to salvage its science-fiction credentials, it then comes up with an impossible solution to the Gamera threat to the human race - I can't tell you what it is, but it would take the entire assets of the developed nations of the world to pull off - it might be better to let the big turtle stalk around and just stay out from beneath his feet.
On top of all this wild nonsense, the American release print, which is the only one I know available, adds on some wonderful campy stuff, like the televised debate about the possible existence of the big turtle, and lowest-budgeted attempt to portray a meeting of the UN Security Council you are ever likely to see - even the one in the Adam West Batman movie looks spectacular in comparison.
There is no way to wrap your brain around this one, so don't bother. A guilty pleasure to the max. And one more important point in its favor - unlike most of the other '60s Gamera films, this one moves along at a fine pace and never drags.
So microwave some kettle corn and munch down - you deserve not to take life so seriously you can't enjoy a bit of fluff like this.
