Photographing crabs can be tricky, they usually flee into the water or hide in the sand when someone gets too close. So approaching slowly and using a telephoto lens may be the best way to get a good shot.
I honestly do not know much about crab species, at most some about common ones, but I have always found the variety of colors and sizes that they have interesting. Some can be larger than a hand, with pliers strong enough to break branches (I don't want to imagine what they can do to a finger).
Anyway, after several attempts, I learned that the best way is to get close enough before they start to flee, slowly get the camera ready and keep getting closer while I take some pictures, so I can even capture the moment when they start their escape.
Well, here I share the result, I hope you like it.