Spirobranchus giganteus, commonly known as Christmas tree worms, are small, tube-building polychaete worms belonging to the family Serpulidae (Wikipedia). Each worm has two Christmas tree like structures that are used for both feeding and respiration. If you move too close to the worm they rapidly retract back into the coral. (In the movie Avatar some of the plants on the alien world behaved in a similar fashion.)
These were shot with the K5 and the fisheye lens. The lens isn’t designed for macro work, but you can still get some interesting wide-angle close-up images.