When the boat sinks with the gang on it, it is clearly a different boat than the one they left on to transport Ben to the mainland.
The bruise on Dr. Richardson's forehead changes size and color throughout the movie.
At 1:44 into the movie you can see the camera crew in the reflection of the aquarium.
Diver visible when creature's cave explodes.
On this supposed isolated island there are roof of other houses clearly visible in several scenes. Also visible are power lines from telephone poles.