An array of small pellet like poo's which are lighter than water and therefore float on the surface.
Are renowned for being very, very difficult to flush away
Man entering cubicle "Ohh what, someone has shit in the pan and not flushed"
Man washing Hands "I did flush actually, about 8 times, but it appears I have had a bout of poolystyrene so it just keeps bobbing about"
Man entering cubicle "Ok.......