Seaweed plants are a type of algae and KELP that grow in the ocean. Algae is a type of plant that grows in water and can range from single-celled organisms to large seaweeds. KELP is a type of large brown seaweed that grows in shallow, nutrient-rich saltwater near coastal areas. Both algae and KELP are important sources of food and nutrition for marine life and are used in many industries, such as cosmetics, pharmaceuticals, and food production.