The term 'playful marine animal' can be summarized as an otter, which is a five-letter word. Otters are semi-aquatic mammals that live in both freshwater and saltwater habitats. They are known for their playful behavior, such as sliding down muddy banks and playing with rocks and other objects. Otters are also highly social animals, living in groups of up to 15 individuals. They are found in many parts of the world, including North America, Europe, Asia, and Africa.