Also kind of cool... video of the predatory tunicate Megalodicopia (not an echinoderm-but closely related to you and me). Most tunicates are filter feeders-but these have modified their "in" siphons so that they capture prey in the bowl-shaped hood...
(and on top of it you get some cool music from Kill Bill!)
The Galiano Glass Sponge Reef in the Strait of Georgia! (Vancover Island)
And More glass sponges!
Some majid ("decorator") crab inside a big glass sponge..