We spent about six hours recording foley today. I love working with the sound team. There is nothing like five guys on four computers in one room working toward one goal. Foley is ridiculously fun. To give a taste, we need to Foley the sound of a very inebriated character peeing in the shower.
Not to put too fine a point on it, but people are used to the sound of urination in a toilet...which loudly resonates in a bowl full of water. By contrast, micturition on flat shower tile sounds high-pitched and wimpy - it doesn't sound believable. Engineering this sound may require a creative mix of noises that have nothing to do with either showers or urination.
I have to stress that the shower-pee sound is really important to the character. The audience must understand that this gentleman is so shnookered, so unbelievably plastered, that he walked past a perfectly good toilet to pee in the shower instead. Before today, I never fully appreciated how many potential laughs in a movie are the work of the sound designer.