The medusial phase of Obelia geniculata exhibits a saucer-like shape, with a convex upper surface and a concave lower surface that includes the central manubrium, housing the mouth at its tip. The disc’s edge is smooth and adorned with sturdy tentacles containing nematocysts. Near the disc’s margin, there are eight statocysts, positioned radially. The mature medusa resembles a floating umbrella or a bell with a bluish-white body, and pinkish gonads are easily observable on the body’s surface.