Behaviour Ideas - Dog going into an obsessive 'trance'

[SquashedToes]

Does anyone have any experience of distracting a dog from a trance-like obsessed state? My dog has couple of obsessions and when engaged in one of these he just goes from the dog we know into a hyper-state. He races up and down barks endlessly and wont be distracted by anything.
Normally he's quite compliant and predictable.
To give you an example, he is obsessed by water (looking in it, not being in it) and when anyone is in the swimming pool (we live in a hot country) he glues himself to the window wimpering, barking racing up and down. It is the same if let him go out to the pool, or if I put him in another room where he can't see the pool.
If I pull him away and distract him with a toy or treat (which he normally loves), he's straining to get past it and back whatever is preoccupying him.
Afterwards he's generally exhausted.

The behaviour in itself is not so much a problem to us, is the racket that goes with it!
Once I had a minor breakthrough and managed to get him briefly to focus on me and rewarded him, but it seems that was a blip!
All suggestions/thoughts welcome!

I have one of these, an obsessive light chaser. When he is in a trance he is very much gone to the world. He will stare obessively at the light for HOURS if I let him never moving a muscle except to try and bite at it He can't eat/drink when the light is around etc as he is too much in a trance by it:

I had two behaviourists who classified it as some sort of stress relief and actually it would be cruel in a way to stop him and both warned that stopping this type of behaviour often leads to other undesirable behaviour as a result such as tail chasing etc. Often they just switch the obsession to something else!

I taught mine to settle and try not to put him in chasing situations, so in your home I would teach him to settle in a crate and then gradually put him in there when you are going to be going in the pool. Cover the cage over so he knows when he is in there it's time to chew a bone or whatever.

There are also medications which can help but I didn't go down this road with mine. It can be classed as a siezure type behaviour in some cases.

Sadly there isn't much you can do though so I sympathise!