It is a question of circumstances whether a ball hit towards a water hazard and not found is actually in the water hazard. In order to apply this rule, it must be known or virtually certain that the golf ball is in the water hazard. If this knowledge or certainty is lacking, the player must proceed in accordance with Rule 27-1.
If a ball is in a water hazard or if it is known or virtually certain that a ball that has not been found is in a water hazard (whether or not the ball is in the water), the player may, with a penalty stroke
a) play a ball as close as possible to the spot from which the original ball was last played (see Rule 20-5); or
b) drop a ball at any distance behind the water hazard, provided that the point at which the original ball last crossed the boundary of the water hazard must be in a straight line between the hole and the point at which the ball is dropped; or
(c) as an additional option, only if the ball last crossed the boundary of a lateral water hazard, drop a ball outside the water hazard within two club-lengths of the point and no closer to the hole than
(I) the point at which the original ball last crossed the boundary of the water hazard; or
(II) a point on the opposite boundary of the water hazard, equidistant from the hole.
The player may, if he acts in accordance with this rule, pick up his ball and clean it or use another ball ( relief in the water hazard ).
(Illegal actions when a ball is in the hazard - see Rule 13-4).
(Ball moving in the water in a water hazard - see Rule 14-6.)
Status: 2018