Does anyone know why some of our poops float and some sink?

Its on your deit like a lot of meats make it float and veggies the opposite

It's all about density.

If your waste is filled with fats (from what 70541 said, meats and oils, etc.) then it will float. This is because your body, while absorbing some fats, cannot digest all of the fats that you eat.

If you eat mostly carbs and fibers, then it'll sink.

I agree with the above answer and have been told before that it does have to do with the fat content of the feces.