Dinoflagellates Most of these are single-celled organisms that look as if they are wearing armoured helmets. They can live in saltwater or freshwater. Many have strange shapes sticking out of them, shaped like horns, spines or wings. Little whips (flagella) beat and move the cells through the water. Most of them cannot produce food, and so they have to take it from their surroundings. Most of them are carnivores, using little harpoons to capture other organisms. Others, which can photosynthesise, live inside the tissue of simple animals such as corals and giant clams in a symbiotic relationship. If the dinoflagellate population grows very quickly, their large numbers turn the sea red, in what is known as "an algal bloom" or a red tide. These can suffocate fish, and their waste products can be poisonous. Red tides have frequently been the reason for National Emergency measures in the USA.