Mysterious Island is a 1961 science fiction film based on the Jules Verne novel The Mysterious Island, which can be read online. The special effects are by Ray Harryhausen (First Men in the Moon, Beast from 20,000 Fathoms, One Million Years B.C., Earth vs. the Flying Saucers, It Came from Beneath the Sea, 20 Million Miles to Earth). There was an earlier version released in 1929.
Youtube has it online divided into 10 separate pieces. Part 1:
part 2, part 3, part 4, part 5, part 6, part 7, part 8, part 9, part 10
The beginning is dark and difficult for me to see the picture on my screen, but I can get a good idea of what the film is like and it lightens up later on.
Moria gives it 3 stars but doesn't have much positive to say. 1000 Misspent Hours says, "At last— a Jules Verne movie that doesn’t totally blow!"