Mr. Goof on Youtube made a video with some cool and relatively unknown things that can be done in Super Mario Galaxy. Like the ground pound move in that game has a homing function, you can hold crouch to skate backwards on ice, and there is a secret button press that can give you a speed boost at the start of Cosmic Mario races. But none of those things are what they claim is the most obscure thing in the game.
The video is titled “Super Mario Galaxy’s Most Obscure Mechanic,” which is a bit wrong. It’s not a mechanic, or mechanism, it’s just a move with no real gameplay purpose. If you stand near water and jump, Mario will dive into the water with a special animation. That’s it. It’s cool, but pretty useless. Still, it’s nice to see it in action.
Here’s the video (7 minutes). Now, go forth and win Mario-related trivia contests, if they happen to ask a question about this extremely specific behavior.