A Little Too Casual

[BC MIST]

In stroke play, a player strikes his ball into an area of casual water that is adjacent to a water hazard. He mistakenly thinks that the casual water is a part of the water hazard. Abandoning the original ball, which he could have easily retrieved, he substitutes a ball, drops it five yards behind the casual water, consistent with the water hazard Rule, and plays it. What is the ruling?

[nokids]

15-2,

If a player substitutes a ball when not permitted to do so under the Rules, that substituted ball is not a wrong ball; it becomes the ball in play. If the mistake is not corrected as provided in Rule 20-6 and the player makes a stroke at a wrongly substituted ball,he loses the hole in match play or incurs a penalty of two strokes in stroke play under the applicable Rule and, in stroke play, must play out the hole with the substituted ball.