Here are photos of two different Green Tube Tunicates (Ascidia sydneiensis) I have been watching develop for the last couple of years.  The one on the left is located at the 57' mark under a ledge on the western canyon at Lea Lea's Leap; the one on the right is in the back of the "meditation chamber" off the eastern canyon at Lea Lea's.  That one on the right is far and away the largest Green Tube Tunicate I have found.  It is over 9" long, though Humann  & DeLoach state that these things are only 2"-4" long.  These creatures fascinate me, in no small part because they are close cousins of ours.  These are actually Chordates, the same phylum which includes all of the vertebrates.  They do have a notocord and close down their inhalent and excurrent siphons when approached.  The youngster on the left is oblivious to my presence, but note how the old guy on the right was closing up on me as I took this photo.  I have tried sneaking up on him many times, but have never managed to get close before he closed on me.