What are my options if my ball is unplayable?

You alone decide whether your ball is unplayable, anywhere on the course except in a penalty area. Each option costs one penalty stroke:

1. Stroke and distance: play again from where you last played. (You can do this even if you haven't found the ball.)
2. Back-on-the-line: drop behind the spot of the ball, keeping that spot between the hole and where you drop, as far back as you like. The ball must come to rest within one club-length of where it first touched the ground, not nearer the hole.
3. Lateral relief: drop within two club-lengths of the spot of the ball, not nearer the hole. If the ball is up a tree, measure from the spot on the ground directly below it.

For options 2 and 3 you must know where the original ball is.

In a bunker: options 2 and 3 must be taken in the bunker. For a total of two penalty strokes, you can instead drop back-on-the-line outside the bunker.

Source: Rules of Golf (2023), Rules 19.1 to 19.3.