What animal is this? [Southern California]

Repost because image didn’t attach properly the first time 💦

I was walking on the beach and came across a very mysterious creature embedded upright in the sand. I’m sorry for an image that’s not too good, I couldn’t get close without the waters rushing up and submerging it, so these are the photos I have. There’s an interesting protrusion I noticed (4th photo), but no leads on being able to ID it myself. Any guesses?