Ceratium is a single-celled organism belonging to a group of algae called dinoflagellates. Ceratium is armored, meaning it has a hard outer coating. Each cell can form two to four horns that help it to float but also slow its movement in the water. This genus is both large and diverse. Ceratium can be found in cold and warm waters and from freshwater to saltwater environments worldwide. It ranges from the low tide mark to about 200 meters (656 feet) in depth. Some species are bioluminescent, meaning they light up the water with a blue glow at night. This dinoflagellate is nontoxic.