swimming lessons

My children take swimming lessons here at our local pool, They go every weekday for 2 weeks at a time. I love them!
Today Luke was working really hard at swimming with his face in the water and he was working so hard that he was exhausted. His teacher asked "Luke, Are you pooped?" Luke, being all sorts of offended yelled "I did not poop! You did!"

I yell from across the pool "Sorry!" and then proceed to hide under a beach towel out of sheer embarassment.

::Sigh::
I guess im going to have to explain what being "pooped" is to my 5 year old.