fisherman (aka kedge, yachtsman, etc) anchor
The old-fashioned fisherman anchor great for hooking rocks. The fluke acts like a pick in softer bottom and digs in, but it will also hook larger rocks or jam into cracks securely being of solid construction. A Danforth is designed for its load to be distributed across the surface area of the flukes. The traditional design can bend easily (happened to a couple myself), and my hi-tensile is worth too much to me to have even tried it to see if it has enough meat for the task. No matter which you use, remember that trip line!