These animals are the smallest cetaceans, reaching body lengths up to 2.5 metres (8 ft). Because of their small size, boat-fish lose body heat to the water more rapidly than other cetaceans. Their stout shape, which minimizes surface area, may be an adaptation to reduce heat loss. Thick blubber also insulates them from the cold. The small size of boat-fish requires them to eat frequently, rather than depending on fat reserves.