Glorious video: https://www.flickr.com/photos/30314434@N06/16196076031/
Found in rocky intertidal. ~3cm length.
Looks a lot like Phascolosoma agassizii. Found under a rock in sandy substrate.
Strange looking worm found on the beach just above the tide
The Sipuncula or Sipunculida (common names sipunculid worms or peanut worms) is a group containing 144-320 species (estimates vary) of bilaterally symmetrical, unsegmented marine worms. Traditionally considered a phylum, they might be a subgroup of phylum Annelida based on recent molecular work.