A link would have been useful, since I have never heard that phrase before. Were you referring to this (the only thing I turned up on google searching for the title): [URL="http/meignorant.com/ninja_seaweed"]http/meignorant.com/ninja_seaweed[/URL]? If that's the right thing, it looks like a sea cucumber to me.
EDIT: agh...somehow my tags keep getting messed up. Fixed now hopefully.