Why are you floating them?
All of the eggs will float because the air cell has expanded. What you are looking for is for the egg to move around (the embryo swooshes around the inside of the sell, and this can be seen when placed in water becasue the egg has nothing to resist the movement.
However it is much easier to candle, using a high intensity/lumen torch, and less risk of drowing the egg or letting bacteria enter the shell
