Can someone explain the joke to me?

Is it just that the lady being recirded is trying to give a clever answer "poisson" because it's already under water and maybe because it rhymes with boisson, but then the cameraman is just giving a straightforward answer (a zebu)?

Sorry about all the Instagram videos, it's about all I get my French content right now. I can stop if it bothers Lemmy users , or at least try to transcribe it instead.

Transcription

Woman 1: Quel animal n’a jamais soif?

Woman 2: Le poisson. [unintelligible for me, perhaps: C’est pas?]

Woman 1: Le zébu.