The term 'Riverbank Romper' is a job description for an Otter, which is a five-letter mammal. Otters are semi-aquatic animals that live in rivers, lakes, and coastal areas. They are known for their playful behavior and are often seen sliding down muddy banks or playing in the water. As Riverbank Rompers, Otters use their agility and strength to playfully explore and investigate their environment. They are also skilled swimmers and can dive deep into the water to search for food.