Mine (Deb's) prefers to be backed into a corner, foot in the sand but up against a large rock or two also. I did prepare a shallow depression in the sand when it came to me, and that seemed to help.
It has moved since, in response to high current. It's now backed up against a rock wall, in moderate/low flow.
HTH, let us know how it does - if this goes on much longer, I may have to "sit" it for you...
