This was inspired by another thread but was my experience awhile back and it has never been clear to what the correct answer is.
Here is incident as best I recall it. I was playing a par 3 about 212 yards in length. Over night there had been a lot of rain and the course was littered with casual water and bunkers that looked like lakes. So as luck would have it I put my tee ball in the bunker guarding the green. Everyone in the foursome saw it splash down and so it was certain the ball was in the hazard (bunker in this case). But the water was quite muddy and try as I might with the rake I can't retrieve the ball because it can't be seen and this is a large and deep bunker. There is no place in the bunker to drop as it literally filled with muddy water from edge to edge and in fact overflowed the edges of the hazard into the "through the green".
So what's the correct procedure here? Is it an unplayable lie even though you don't know the balls exact location and if so where do you drop? Is it a lost ball (you know it is in the bunker somewhere)? Maybe this is casual water because the bunker isn't designed to be a little lake and I should get "free" drop in front of the bunker?
Just so you don't ask I decided it was a lost ball and went back to the tee but I am not sure that was the right call but it was the consensus of the foursome.