Generally speaking, marine organisms found along middle Atlantic shores are not considered threatening to people. However, some of these animals can cause problems, either upon simple contact with the skin, as in the case of some jellyfish, or through careless handling. In addition, larger inhabitants of coastal waters (such as sharks) must always be treated with great respect because of the danger potential and their unpredictable nature. Descriptions of nuisance and potentially harmful organisms are therefore provided to help coastal residents and visitors become more aware of how problems with such marine animals might develop, how they can be avoided, and how certain injuries should best be treated if they occur. Animals described include: (1) jellyfish (stinging or sea nettle, lion's mane jellyfish, moon jelly, portuguese man-o-war, mushroom jelly, comb jelly); (2) sharks (sandbar, bull, dusky, tiger/hammerhead, sand tiger, Atlantic angel and mako sharks, and the spiny dogfish); (3) stingrays (bluenose stingray, cownose ray, roughtail stingray); and (4) unassuming problem fish and crabs (including toadfish, puffers, bluefish, black sea bass, blue crab, and others). (JN)