Ugh that story horrified me. If I remember right, some celebrities and directors were having a party on the Jeopardy soundstage with some child "entertainment". Heather O'Rourke was sent out in a swimsuit to dance for everybody before being taken backstage by the party hosts. Shortly afterward, she died of supposed intestinal stenosis.

Also, the skeletons are real because the studio wanted to save a buck and it was more expensive to use props at the time. They didn't tell the actress she was in the water with actual corpses until they were done filming.