By Tanya Waterworth
According to scientists, crocodiles have been on Earth for some 60 million years.
So what's their secret to survival?
BBC reporter Jill Fullerton-Smith met zoologist Adam Briton, who questioned how crocodiles could lie in bacteria-filled water and yet their injuries healed quickly - even though they could have been seriously injured in a fight.
In a report on the BBC/Open University website, Fullerton-Smith said she set about making a film on finding the answer.
"Why is it that a crocodile could heal in the same bacteria-filled water that would cause us to die from infection if we had the same sort of wound?
"There had to be something amazing in the crocodile's immune system, and we very quickly found out that there is a little string of peptides, which were only discovered very recently in the last eight or nine years, and they are a powerful mechanism for fighting bacteria.
"I think we waited five months for the results to come through, when we got the call to say that they had found it."
Rozina Ali, a plastic surgeon, explained that "anti-microbial peptides are small proteins - lots of amino acids put together in various configurations".
"The interesting thing about them to medics is that they are anti-microbial, which means that they work against microbes - and microbes means bacteria, fungi and viruses.
"As far as we know, there aren't any organisms which have any resistance to these anti-microbial peptides. It's something that is going to have a lot of importance in the future in medicine."
A company, Repcillin, which harvests crocodile oil to make a balm for skin complaints, states on its website that crocodile oil has been used as a natural remedy for centuries as a skin healer.
"Crocodile oil that has been analysed shows it is rich in Omega 3, 6 and 9, which are known to be beneficial for skin complaints.
"Other beneficial properties found were a number of rare essential fatty acids which were found in high concentrations," states the website.
And just outside Durban, in the picturesque Valley of a Thousand Hills, is a great example of a crocodile being able to outlast and outlive.
That's Junior, the 4.3m Nile crocodile that lounges around as head honcho of the crocodile kingdom at PheZulu Safari World.
Lady-killer
He's lived for more than a century, and is a real lady-killer - in more ways than one. His passion is so great that he has, in the past, inadvertently drowned some of his partners.
Croc handler Tim Korb said the monster reptile was born in the Okavango swamps in Botswana in 1905. Junior will be 106 in December. He weighs approximately 600kg and, despite his age, still has a lustful eye for the ladies.
His current paramour is Juliette, who keeps him in order. She's already bitten off three of his toes and a piece of his tail. Juliette has also killed two other crocodiles.
Korb said: "But he loves her, he's like a big puppy, really.
"He's still quite a stud muffin and we can hear him from 500m away when he starts courting the lady crocs."
And, according to Korb, Junior is likely to get five females responding to his calls at any one time.
Crocodiles breed in winter and female crocs will often end up fighting for mating rights and nesting sites to the point of killing one another.
While Korb says it is this deadly temperament that has helped ensure the survival of the species through many centuries, he also credits their biological advantage, the now recently proven anti-microbial nature of their fat, that promotes fast healing.
"Even though crocodiles have a brain the size of a peanut, they are extremely clever, especially when it comes to a killing strategy.
"They are calculating, cold-blooded killers and will eat younger crocs, if necessary, to survive.
"But they also have the strongest immune system known to man, as their fat contains a natural antibiotic and they heal very quickly," said Korb.
"This antibiotic is said to be particularly good for skin disorders and I know one guy who eats it on toast as a remedy for his gout."
Fortunately for Junior, he doesn't appear to suffer from such mature maladies, but he must watch out for Cuddle - aka the Italian stallion - in the neighbouring croc pool and who, at a mere 25 years old, has 19 ladies waiting on him.