Freshwater accounts for only three percent of the world’s water - the rest is saltwater. But despite that tiny amount, freshwater habitats are homes for more than 100,000 species of plants and animals. Fish living in freshwater habitats have plenty of company. Snails, worms, turtles, frogs, marsh birds, mollusks, alligators, beavers, otters, snakes, and many types of insects live there too. Some unusual animals, like the river dolphin and the diving bell spider, are freshwater creatures. Plants such as algae, cattails, water lilies, and aspen and willow trees help keep the water clean by using their root systems to filter pollution and excess nutrients from the water.