Ok, it looks like I stymied everyone. What I posted was part of a picture of a Sea Pen, taken at the Oregon Coast Aquarium.
http://www.aquarium.org/jellies/relative.htm

The Sea Pen is a soft coral, so I think Kort came closest to guessing so Kort, tag, you're it!

I was really conflicted about how much of the original pic to post, and I think I posted too small a piece. But it sure was fun to see the interaction as people fed off each other's guesses and my replies. Here's the whole picture as I originally took it. It's through the glass of the tank, so it's not as clear as I would like, but that's just the way it is.