Destination Inner Space (1966)
Strange goings on at the site of an experimental underwater laboratory as a mysterious object of unknown origin is detected in the area. A group of researchers investigate and come face to face with the object, a large automated extraterrestrial probe. They board the craft and discover a small object at first considered to be some sort of instrument package, which they take back to the lab for closer inspection. It is then that events take a turn for the worse. Revealing Mistakes: You can see the reflection of the diver's mask behind the creature's eye sockets. In addition, when the creature attacks the support ship captain, he is wearing boots. Later, as he is swimming, his feet are webbed. As he swims, you can see the outline of his air tank in the hump beneath his dorsal fin.