His grades were below sea level
A tuna.
Fish
By son.
He needed to see if how fast his grade dropped broke any laws of physics.
A nun with a javelin in her throat. (The only joke I can ever recall when asked for one. Told to me by my art teacher in Grade 11. Needless to say, he was my favourite teacher)
Submitting a stool sample.
He accepted eternal returns.
Sea Level.