I had to been about 8 when I saw this movie. It probably was made between the 50's and 70's.

Snipits of the movie I remember:

A group was on a island
Captured by island natives
A small boy escapes in a small crevice. They tie a vine around his ankle and he drops down a pit swinging wider and wider across a ravine.
Crazy old man laughing as the boy is swinging.