I think he says we've stopped.
3 seconds sound clip from the Finding Nemo movie soundboard.
You can hear this line at 01:11:33 in the Blu-ray version of the movie.
Quote context
[...]
- Huh. That's a funny thing to promise.
- What?
- Well, you can't never let anything happen to him. Then nothing would ever happen to him.
- Not much fun for little Harpo.
- I think he says we've stopped.
- Of course we've stopped. Just stop trying to speak whale. You're gonna make things worse.
- Oh, no. Look what you did. The water's going down. It's going down!
- Really? You sure about that?
- Look. Already it's half-empty.
- Hmm. I'd say it's half-full.
[...]