Im not being funny here but have you tried unscrewing the shower head and making sure there isn't a decomposing fish inside it? My knowledge of student life is not great but I have watched a few american 'frat house' style films in my time and that sounds like a prank someone might play.
Infact I recall in one such film someone put clothes dye inside the showerhead.
Infact I recall in one such film someone put clothes dye inside the showerhead.