The Eurasian otter is a long, slender, semi-aquatic mammal with dark brown fur on its back and creamy fur underneath. Its body is highly adapted for life in the water. Dense bones reduce buoyancy, helping it dive and swim efficiently. Compared to the North American river otter, the Eurasian otter has a shorter neck, a broader face, more space between the ears, and a longer tail. Across most of its range, it is the only otter species present, so it is rarely mistaken for anything else. Adults typically measure 57–95 cm in body length, with an additional 35–45 cm tail. Females are usually smaller than males. Most weigh between 7 and 12 kg, though large, older males can reach 17 kg. An unverified record suggests a specimen may have weighed over 24 kg.