Since March 29, 2009 I have been scouring the internet and college biological heads in search of an ID. While shooting tide pools at at the Mana Kai Maui Resort the Keawakapu Beach, Maui, with my 180 Macro (1/500 sec @ f/8.0,ISO 400) I moved a rock and disturbed this critter. It is about 4-5 inches long, and moved surprisingly quickly with a peristaltic bulge that would move the length of the grey portion of the animal from the end with the white-sh appendage(s). You can see the bulge forming in the first frame (043) near the white appendage(s) It moved with a flopping action that did not seem to be directional but it disappeared fast. These three images were captured three seconds apart and was gone. Any ideas?