I finally remembered to bring a chair with me today. One of the problems I encountered was that the legs were sinking really far into the sand so I tried to put some large rocks under the legs to keep it from sinking in. That worked, but on my first try, the chair slipped off the rocks and promptly launched me into the wet sand.
I finally gave in and just let the chair sink as far into the sand as it would go. Once there was only 8 inches of the chair still left above the sand, it finally stopped sinking. Last step was just to get the pose right and snap the picture. I also used my phone to trigger the camera, as I did yesterday. I decide that the most dramatic poses had my face super close to the sand and my legs bent upward at different angles.
Canon EOS 6D
Sigma 50mm f/1.4 @ f/1.4