There is a great deal of controversy over the use of subway cars as artificial reefs. There shouldn't be. Subway cars are fish condos. They are the perfect size and shape to provide homes for all sorts of fishes, as well as large attachment areas for other organisms. The fact that they come complete with large door and window openings is even better. Most reef materials, such as ships and barges, improve with age because they open up, allowing easier access to the interior. Indeed, some of the most barren reefs I have seen are those that are completely intact, since they offer little shelter.
Echinoderms ( literally "spiny skins" ) are among the strangest animals on the planet. They start out as bilaterally symmetric larvae but grow into a 5-way body symmetry as adults. Some species show six, seven, or even higher levels of symmetry. Worm-like Sea Cucumbers have re-evolved a bilateral body plan over the underlying 5-way plan. Because of certain developmental traits, it is felt that despite their strangeness, echinoderms are actually more closely related to chordates than any other group.