Saw several of these on night dives in Utila in late December. Reef Creature ID doesn't mention these, which are about 15 inches across.
looks like a swimming crynoid to me... sounds like it's a big one.
REEF Headquarters | P.O. Box 246 | 98300 Overseas Hwy | Key Largo, FL 33037 | USA Phone: 305-852-0030 | Fax: 305-852-0301 | email: firstname.lastname@example.org