I can legally carry a 100mm long blade which is just short of 4 inches. I do work in hostile environments but don't carry a pistol because of the restrictive laws and because carrying a handgun in said environments make you a target. Tough choices...
If you can carry a fixed blade while camping or hiking, look at the Puma Hunter's Pal or the Fallkniven F-1. Fallkniven also makes the lockblade U-2, with a blade short enough to let it be carried in many Euro countries with tough knife laws.
My Spyderco Delica is by the computer today, and the blade measures 3 and an 8th inches. It's the smallest knife I'd want to use for defensive needs, but the U-2 will also do some nasty slicing if need be. It's extremely sharp. Be advised that if you have to use it on an animal, a man in Texas who used one (Delica or similar Spyderco) on a cougar wasn't able to stab deeply enough to achieve lethal wounds, but the cat attacking his young son did flee after sustaining some wounds. I'd try to cut the throat of any sizable opponent or go for the femoral artery in the leg. Some people don't think about how lethal that is.
On a croc, you'd probably have to stab it in the eye to achieve penetration and a serious wound. I know of a case where that happened, after a man there came to the rescue of another angler.
Of course, most Swiss Army knives will meet the size limit. And they will seem logical candidates if you tell a cop that the knife is for general utility use.
Can you carry a longer knife while hunting?
Do you encounter dogs or baboons? I knew a woman in Simonstown (Simons Town?) who had trouble with near urban baboons trying to get into her house. I know they attack people, and have really dangerous teeth. That's not especially far from Cape Town. Is there still a naval base there?
Isn't carjacking a big problem in most South African cities?
Oh: if the Benchmade Model 705 is available there and the blade is short enough, it'd be a prime choice. I have the same basic knife in the larger size, Model 710, with about a four-inch blade. I love it, and if I had the money just now would buy a 705 for days when I might need a smaller knife to meet local laws. I think the blade length is about three inches. See Post No. 69 here for a photo.