Click on the croc heads when they pop out of the hole. Sometimes they might tease you by only coming up half way, or sometimes they'll hide for long periods of time. Try to whack as many crocs as possible!
For those of you who've seen the flash intro on my site (featuring a crocodile getting hit on the head with a broom), this is a game version of the popular "Hey kids! Ooowwwwwch!" thing associated with Baronvonbrunk.com!