Euglenoids are green or brown and swim with their flagellum, too. They are easy to spot because of their red eye. Euglenoids are microscopic and single celled. Dinoflagellates have a flagella and can swim in open waters. They are microscopic and single celled.
Diatoms look like two shells that fit together.
They are microscopic and single celled. Algae are photosynthetic creatures. They are neither plant, animal or fungi. Many algae are single celled, however some species are multicellular. Many, but not all of red and brown algae are multicellular.