Continuity mistake: When the two men are carrying water up to their new cave home (via a home made elevator), one of the men is holding two buckets of water. In the shot where you can see the sea behind them, this man hands the second man a bucket of water, which he takes. In the very next shot, from inside the cave, the first man has both buckets and again hands the other man the bucket of water. (00:48:35)
Continuity mistake: The police that come to the aid of the professor are driving an older Ford when they approach than when they arrive to help. The car is a newer model in the later scene.