desensitizing help needed please

[blood_magik]

My horse is terrified of the water tray
Whilst he will quite happily jump it if it's being used as a filler (ie there's a fence over it), he panics when I ask him to go near it and does the whole snorty piaffe horse-eating monster thing

Last night, I ended up on the floor holding his bridle while he buggered off to the other end of the school Partially my fault, as I should have known better but never mind - it happens to the best of us and was a good reminder to SIT UP!
He jumped it after the fourth refusal and a smack on the bottom (I felt he was taking the mickey at this point).

So.. How can I make it less scary? I've tried treating him when he takes a step closer to it but he gets to a certain point and then tries to stretch without getting any closer.
He will eat from it but not walk over it or touch it with his hoof.

Costco victoria sponge available

 

[be positive]

Why do you need him to walk over it?
I would make it into a very small jump and go over it then drop the pole one side ,then over it then drop the other side until you can take the pole away.

 

[Miss L Toe]

Practice groundwork with a tarpaulin and with stable mats and anything else he reacts to, also do a bit more hacking where he has to look where he is going, he should be trained to do leg yields. He is perfectly sensible not to put his feet in a very scary thing.