Elements I can recall:
This film was on VHS in the 1990s. I found it in a large collection of live, action-adventure Disney-made movies but it is not necessarily itself a Disney film--it just fit in thematically with the others.
It involved a brother and a sister (the sister with long, thin, brown, 70s-style hair) on an island. The two lead actors were prepubescent. There was a man in his 30s with amnesia who is later revealed to be their long-lost father. Their mother is dead and her picture is in a locket; it is this locket that awakens the man's memory. The locket is lost at the bottom of a pool of water below a waterfall. There is also a very large quartz crystal hidden in a cave behind the waterfall which the film's narrative claims is a gigantic diamond (that part sounds like The Rescuers, right?). The film may have involved pirates. I only ever saw this movie as a child and no one I know has seen it since. Based on what I remember of the movie I feel it was likely made in the 1970s. The collection of films this was in also included many dubbed cartoons and live-action family adventure films imported from Europe, so it may be a European film that was dubbed (I would have been too young to recognize whether a film was dubbed or not).
https://preview.redd.it/hypiplqq05v71.jpg?width=4032&format=pjpg&auto=webp&s=18c5f8fbb3f36973d4b82da4738604d7874072b2
OK so that tune is an LDS hymn....or is it? Are most LDS hymns by LDS composers or are most of them reinvented from other composers?
