Yep I would say Orca (killer whale).
I was checking out Cathederals at the back of Rotto whilst getting ready to head out for a solo surf a few years back when I saw a huge fin sticking up almost vertical just behind the break, decided to give it a miss

. I could only think it must be an Orca but wasn't sure if we got them here, I started telling the local ranger who had lived on the Island for years and he told me that they were often seen around this time of the year and that they ambushed and picked of the weaker whale calves as they made there way South and headed around the West End.