pool or river?

On Sunday we were heading up to visit Uncle Josh, Aunt Abby and Aunt Amy. Since they live in Parkville, MO, we have to cross the Kansas River to get to their house from ours. The following is a conversation that I had with Gillian as we were on the bridge over the river:

Gillian: poo, daddy.
Me: Did you go poo poo?
Gillian: No. Poo, daddy
Me: Are you full? (some clarification is in order here. Gillian's new 'excuse' for not doing something that we ask her to is that she's "poo". It took us forever to figure out that she is telling us that she's full, as in, I've eaten too much and I'm full. The gestures she gives when telling us she's "poo" is hysterical).
Gillian: No. POO, DADDY (becoming increasingly more agitated).
Me: OOOOOOOHHHH. Do you see a pool?
Gillian: ah (pronounced like 'yeah' without the y -- which is her version of yes).
Me: Well, that's actually a river, Gilly. Not a pool. You can't swim in rivers, but we swim in pools.
Gillian: Oh ah. (her version of oh yeah, i knew that)