This got way to complicated. Sharks tails are made vertically, but move horizontally. And vice versa for whales. Why im right in this case is because its due to how the tail is being built, so movement is irrelevant. Direction of fin is important in its creation, not movement. Can we at least all agree that that shark in the picture has the wrong tail? xD

@Mabzino just sayin, up to down and left to right definitely sounds like movement

But we were talking about the picture?

(Somebody please re-name this thread to: Discussing Tails)