Why does the few crocodiles nearby not attacking the zebras?

I was wondering the same thing about the crocs. Perhaps it is because there are so many zebras that attacking one would result in getting attacked by the rest of the herd and is thus not worth it? Do the zebras giving the crocs a staredown have anything to do with it?

The crocodiles have already eaten their fill just a few days earlier when the crossing first started. So this is one of the reasons why they don't attack, the other is that only a couple of the crocodiles in this area of the river are actually skilled enough to take down a zebra - the others are too half hearted in their efforts, and then they all fight for the same zebra if one is snatched by the stronger two. The zebras would not try and attack the crocodiles.