I am not a naturalist, but I do observe and there seem to be two general categories of sand crab activity on a beach. There are the dome shaped dwellings most sand crabs construct; and then there are these wild geometric patterns a minority of crabs create. These latter have more in common with photographers than others of their species and so I give them space on my blog.
Canon PowerShot G16
1/800 second
F/1.8
ISO 80
7 mm