Aquatic rodents are semi-aquatic mammals that live in or near water. The most common aquatic rodents are the NUTRIA (6 letters), muskrat (7 letters), COYPU (5 letters), musquash (8 letters) and otter (5 letters). NUTRIA are large, semi-aquatic rodents with webbed feet and a rat-like tail. Muskrats are smaller than NUTRIA and have a thick, glossy coat of fur. COYPU are also known as river rats and have a round body and short legs. Musquash are large, semi-aquatic rodents with long tails and webbed feet. Otters are the largest aquatic rodents and have thick fur and webbed feet.