The Great White Shark is a species of mackerel shark which grows to over 6 metres in length. It is characterised by its size and streamlined body shape. It is counter-shaded, and is grey on top and white underneath, with serrated teeth and a dark eye. The lobes of its powerful tail are more or less equal size, which help it to reach a top speed of around 40 km/h. It can be distinguished from its close relatives, the Mako sharks (Isurus spp.) by its more robust body shape, larger size and its triangular serrated upper teeth. The Great White Shark is extremely dangerous, and should be avoided if encountered. While attacks are rare, it has been responsible for unprovoked attacks on humans, many of which have been fatal.