Gotta go, gotta go!

Have you ever peed in the swimming pool?  Of course you have - don't lie!  Well, here's a fact that may make you think twice before doing it again - urine can combine with chlorine to produce toxic chemicals.  Fortunately only in very small amounts, but if it's a very small pool, or everybody decides to relieve themselves simultaneously...  well you get the idea - so best tie a knot in it!