Andrew Anderson carrying a harpoon on board a factory ship, where caught whales were cut up and processed for their oil. The head of the harpoon is a grenade that explodes once it's inside the whale. The explosion is detonated by a vial of sulphuric acid, found inside the harpoon head, being crushed by the four barbs opening. The barbs only open out when they are dragged backwards through the whale's body, which only happens once the rope attached to it comes under tension. The shaft of the harpoon can also swivel once the barbs have opened out.