The dwarf sperm whale is the smallest of the whales and is even smaller than most of the dolphins. It has a square head and moves relatively slowly in comparison to dolphins. It is extremely similar to the pygmy sperm whale and is usually indistinguishable when spotted at sea. Its skin is dark blue to olive brown become paler and sometimes pink on its underside. It has a taller and more pointed dorsal fin in comparison to the pygmy sperm whale.