Sea fans (Gorgonia ventalina and G. flabelluin) grow in patches at depths of 2 to 10 m on the seaward reefs of the Florida Keys. The sea fans in any particular patch appear to have a preferred orientation of their fan “?�blades.” ThA©odorand Denizot ( 1965 ) have noted this phenomenon and concluded from the parallel orien tation of algae and gorgonians that the orientation of all fan-shaped sessile organ isms is perpendicular to wave motion and that it may result solely from hydro dynamic phenomena. We have asked the questions, “?�To what extent do sea fans on Florida reefs show preferred orientation ?“ and “?�What can be inferred from the morphology of the sea fan and from the habitat concerning the mechanism that brings about this orientation ?“ METHODS We worked on several coral reef sites on the upper Florida Keys over July and August, 1966, and put in more than 25 man-hours making observations and photo graphs while using self-contained underwater breathing apparatus. We spent at least one fifth of this time diving through twilight hours and into darkness. We exposed twenty-four 50-foot rolls of Super 8 mm movie film using a Kodak M-6 camera with close-up lenses to record observations and to aid further study of the activities of soft and stony corals. For measurement of the orientation of sea fan blades to points of the compass, a waterproof compass was mounted in the center of a 12” square white plastic board. Holding the board horizontally we then placed a side of the board flat against the blade of a sea fan and made a pencil mark on the board at the north arrow. We measured maximum height and breadth of the fan to ±0.5 cm with a 30 cm rule and recorded these figures next to the orientation mark. We recorded these data for every fan in each patch studied. We surveyed patches in the following places: