Hydras are simple invertebrates. They live in the fresh water. Their body is radially symmetric. They have a central cavity that serves to both take in food and expel waste. Being Cnidarians they have stinging cells on their tentacles. They are hydrozoa, and belong to the same order as the polyps. Most hydras are microscopic in size. Hydras can be found in almost any unpolluted body of water. Hydras reproduce in an asexual way called budding. In budding, the offspring forms as a lump on the parent and eventually becomes big enough to break off and live by itself.