This is not an easy question, because as far as I could find on the Internet, there are several opinions about the floating poops. I could find that the floating poop has to do with the fat/fiber you eat from food; nevertheless, other people say that floating poop has unusual high gas content. Sometimes this gas does not have a chance to collect into a fart bubbly, but remain dispersed in the feces. The poop then comes out foamy, and has a lower density than water.

Let me tell you that when I was working at a children's hospital, long time ago, I used to frequently see some child's poop at the Care Unit, and those who were under high fiber diet had floating poop. I believe that this poop has to do with the fiber content in it. Usually eating food with fiber content is healthy for our body.