Risso's Dolphin
Grampus griseus

Risso's Dolphin is easily recognisable when surfacing due to its lack of beak and at up to 4 metres is the second-largest dolphin in Australian waters (only the Killer Whale is larger). They are often covered in scars, which give the coloured lines seen on their skin. They are often seen in pods of more than 20. Unlike Common and Bottlenose dolphins, they don't tend to ride the bow waves of ships, but will come near out of curiosity.
 

1-2: Sydney Pelagic, Tasman Sea, NSW, 12/03/2011.