Rules - a question

I came across this in a social game.

The green was behind a large pond/lake.  There was no marking either red or yellow on the pond, and the local rules are silent on its status but there is a drop zone you 'may' use.

The green was much higher than the pond and to the back of the water hazard, to stop the green slipping into the water, the bank was supported by creosoted wood.  I am sure there is a name for such a wooden bank support arrangement, you see it a lot.

The player hit the ball on to the green but it spun back very gently and slowly came to rest on the outside of one of this wood, which protruded a few inches above the grass.  There was no marking on this wood.

The player could not make a stroke at the ball. 

So, was it an immovable obstruction (question one)?  I think yes.  Was it 'in the hazard' (question two)?  Surely it has to be, and so effectively the player had to go back to the other side of the water, no doubt to the drop zone but not necessarily ('may' is in the local rules) and play his ball under a one shot penalty. 

Am I right?
 

The alternative opinions were:  a.  It was an immovable obstruction outside the hazard (free drop); and b. Having carried the water it was a lateral hazard 'on that side' and the player had to take a penalty but not necessarily go to the drop zone the other side of the water.

Martin,

I have come across this type of structure many times.

It all depends on how the Club designate them. They can be inside the Hazard, or be either an Immoveable Obstruction or an integral part of the course. It should state on the Local Rules how to treat them.

The use of "may" has to be there because you can always play the ball when it's in a Water Hazard.

TheLyth