Two men hunt the rogue crocodile that killed both their wives. One wants to save it, the other wants it dead!

Just because the croc is protected here, are they protected everywhere?
If not, bang goes your whole 'rogue croc' element. Add that to the script, not the logline as you may lose potential buyers.
Something else to consider when writing the script, can the film be made without to much cost?
The best logline in the world won't help if portions of the script require a crew to be in croc infested areas, cause then the costs start escalting.

I first wrote tale in novel form more years back than I care to remember. The thing is, it is set in Australia. Here in oz the croc is a protected species and is more likely to be relocated than killed in the event of an attack.The theme seemed to work well enough in the novel but in trying to turn it into a movie, I must admit I have been struggling. Now here you go and slap me over the back of the head with the friggin obvious.
I recently asked a producer what to do when the antagonist appears to be taking over the story, his reply was "Interesting question, why don't you put it up in a forum."
Now I'm thinking that I have been so stuck on the original story that I couldn't see the forest for the trees.
Another draft here I come.
Thanks (i think)

Cool, now you have a main character. But try to sum it up in one sentence. A logline should be around 25 words or under...

Check out the "How to Write it?" section of https://loglines.org/howto/ if you haven't already done so.

I don't like the "save it" guy being the main character. The crocodile is clearly dangerous and taking human lives. Saving a killing monster because your crazy dying wife made you promise to sounds like something a "screwed in the head" villain would do, not a hero.

The "kill it" guy's motivation is more credible and relatable. I understand the need to avenge the wife he loved, and to stop the monster taking more lives.