Ball in Bunker Full of Water
Question: - My ball has landed in a bunker that is full of water. Can I have a free drop, outside the bunker, if the entire bunker is full of water?
You can, however have a drop, without penalty, within the bunker at the spot that affords maximum relief. This spot must not be nearer the hole.
So what does maximum relief mean?
The spot providing maximum relief might be such that the ball will be in shallower water. (R&A Rule 25-1b.(ii)(a)). also (R&A Definitions of Rules of Golf 25-1b/6)
If complete relief is not available within the bunker the player may under penalty of one stroke, drop a ball outside the bunker keeping the spot were the ball lay directly between the hole and the spot on which the ball is to be dropped. (R&A Rule 25-1b(ii)(b)). (There is no limit as to how far behind the bunker the ball may be dropped.)
A further option
You could also, under penalty of one stroke, play from the original spot.(R&A Rule 28a)