The term 'Riverbank Animal' can be solved by the five-letter word 'Otter'. Otters are semi-aquatic mammals that live in rivers, streams, and other bodies of water. They are known for their playful behavior and are often seen sliding down muddy banks or playing with rocks. They are also skilled swimmers and can stay underwater for up to eight minutes. Otters have thick fur to keep them warm in cold water and webbed feet to help them swim.