The bottom one is a species of Parasesarma, one of the costal ones that need brackish water to complete there life cycle, but the adults live all there lives in fresh water, they are dependant on a soil type to dig the holes in. or they dig under rocks, the males can be bright yellow
Middle one is the Tiger crab, Holthuisana Tigerensis it is a protected species that live on a northern branch of the Mitchel river called the Alice river, very common where it occurs.
Top one is Holthuisana agassizi, a wide spread species across the Cape and every separated area has a different colour.
The family name Holthuisana has been changed, I have not kept up with it.
There is lots more nice species, the only one I ever have in numbers is the top one and I just sent heaps off to a wholesaler down south, so you may see some in a shop near you?? and don't believe the story that seams to attach to the purple one, the story they need to get out of water its BS, the bottom one HAS to get out of water as its costal.
Time to stop, I could rave on and on
Bob