Two options - either drop and hit from the original spot, or, keeping the hazard between you and the hole, draw a line from the flag through the spot the ball went in, and drop anywhere on that line, as far back as you like.
Yes, it sucks. The thing to remember is to keep the hazard between you and the hole.
How do you mean? If I get over the hazard and it rolls back in, what do I do then?
Brian
I'm not sure that mdscpa hasn't confused the issue. I think he means first time not when you are playing you recovery stroke.
The point is that if you end up in a WH the relief options in effect require you to clear it with your recovery stroke.
The additional options for a LWH allow you to play from either dide of the hazard which may mean tat you don't actually play over the water.
Comment