If they had released this movie in Britain, it would have likely become one of the infamous video nasties. It has all the elements: low production costs, natives in various stages of undress, animal abuse, shark attacks, cannibalism, torture.
It just didn't really cross the line, however. The torture was not overtly explicit, the cannibals were never shown eating their victims, the undress was not excessive.
If it had come out a month later and starred Steve McQueen and Dustin Hoffman, instead of Jim Brown and Christopher George, they might have named it Papillon, and given it an Oscar or Golden Globe nomination. But, this is a Roger Corman production, so it is the R rated version of Papillon.
Paul Richards, as Major Marteau, the head of Devil's Island, gave the best line after they tortured a woman to get information on the escaped prisoners: "She doesn't know any more. Anything else would be lies." He knew even then the uselessness of water-boarding.
Great ending!