Killer Killer Achievement
Harpoon a killer whale.
Killer whales are one of the toughest animals to hunt, so ensure that you have fully upgraded your rowboat armor, harpoon strength, and harpoon storage. There are two on the map and will be indicated by a white icon that is a silhouette of a killer whale. The locations are (582, 338) and (120, 496).
When you are on location you can hold down to initiate the harpooning mini-game. If you fail, you can restart over and over again until you are successful without any type of penalty. Pay attention to your crew in the boat as they will warn you before the killer whale is going to hit the rowboat. If you successfully stick the killer whale with a harpoon it will interrupt his attack. The achievement will unlock at the cut scene as the killer whale floats to the surface.