You can declare the ball unplayable at any place on the course, apart from in a water hazard.

Unplayable Lie Penalty Drop Options Playing from Point A going to Point B ball ends up in a bush at Point C.

You can then under a penalty of 1 shot either

1 Drop a ball not nearer the hole and play from where you last played or teed up if played off a tee

2 Drop a ball not nearer the hole within 2 clubs lengths from where the ball is

3 Drop a ball behind the point where the ball finished, keeping that point directly between the hole and the spot on which the ball is dropped. There is no limit on how far you can back.