Rules
You're 236 yards out on a par 5, and you hit your 3-wood flush. But as it tracks toward the green–DOINK!–it hits a power line and bounces into the rough. What do you do? According to Decision 33–8/13 in the Rules of Golf, a course can enact a Local Rule allowing for the replay of the previous shot without penalty.
Note: You don't have the option of playing the ball from its new position. However, if the course doesn't have this Local Rule, play the ball as it lies.
POP QUIZ
Q: You think the ball you just hit is in a water hazard, but you're not sure. Can you play a provisional ball?
A: Yes, but if it turns out the ball went into the hazard, the provisional ball must be abandoned, and you must proceed with the original ball.
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Rule 18
The ball moved, but is it a penalty?
First, know the definition. A ball is deemed to have moved only if it comes to rest in a new place. But a ball that oscillates has not "moved." If the ball moves after you've addressed it (outside a hazard, "address" means taking your stance and grounding your club), then add a penalty stroke to your score and put the ball back. There's no penalty if it is moved by an outside agency (a spectator, squirrel, etc.) or as a result of actions such as searching for it in a hazard, removing an obstruction or a loose impediment on the green. But you still have to replace it. / Shuhei Matsuo