PEEPs will float on their own, but as a PEEP has more weight than surface tension can break (which is why the boat can move with soap power, the soap alters the surface tension of the water and forces the boat to move), you will have to modify the shape a bit to get this experiment to work.
First, try the experiment with a whole PEEP. Put a bit of soap between the ears and let it loose in the water. It may move a bit, but it won’t look magical.
However, once the shape of the PEEP is altered, it will move much faster. Trim the ears to a narrow point close to the head, as in the image below. Cut the body completely off and trim the chin to a sharp point.
This will make the PEEP light enough to be moved with surface tension. If you have ever tried the milk surface tension science project, this is a similar idea.
Add a drop of soap behind the ears and set the PEEP loose in the water. It should float across the water at a pretty good clip. If it doesn’t, your water may be too soapy.
Try exchanging the water with clean water and try again. It took us several attempts before we got our experiment to work properly.