I try to play by the rules, as much as playing by the rules is practical. Practical is usually a question of pace. If a player in my group hits two consecutive tee strokes OB, we employ the mercy rule. Take a drop where the last ball went out. Have mercy on your playing partners.
I had a situation Sunday playing with an unfamiliar playing partner, I failed to clear the water hazard hitting to the green off the tee on a par three. I was not aware of a drop zone, and was really wanting to take the stroke over, so I prepared to re-tee and hit again. My playing partner said I could not re-tee, I could only drop and hit off the teeing ground or some point forward towards the water hazard. Not knowing the rule or desiring to debate his call, I went to the front of the tee box, took a drop and hit again. I got over. No big deal. I was more intrigued by his call than anything. I did not know if this was correct or not, but it sounded right.
Fast forward an hour tothe final par 3, also hitting over water. Rules guy shanked a ball into the water. This was a little different because we did not see a splash, blocked by the crest of the hill. It was fair to say, we were virtually certain his ball came to rest in the hazard, with no drop zone. He walks back, declares a lost ball and re-tees.
A learning golfer could carry a rule book and I'm not sure he would definitively make either call quickly. I would love to hear some opinions, including the mercy rule.