The first is the polypoid stage , when the animal takes the form of a small stalk with feeding tentacles ; this polyp may be unable to move around , living on the bottom of the ocean or it may be free-floating . The first is the polypoid stage , when the animal takes the form of a small stalk with feeding tentacles ; this polyp may be sessile , living on the bottom or on similar substrata such as floats or boat-bottoms , or it may be free-floating or attached to tiny bits of free-living plankton or rarely , fish or other invertebrates .