I had an 18hh Clydesdale who was terrified of even the tiniest puddles, go figure! I finally broke him of his fear by having my friend's trusty, calm Standardbred lead him through them. He pranced through them like a parade horse LOL but he went through the puddles. My friend also had treats in her pocket and we would stop in the middle of the puddle, give him a treat, then continue walking across. (We had a huge storm that flooded a lot of our trails at the time so we had huuuuuuge puddles to walk through.) He eventually found out that the water wasn't so bad because he'd get a treat every time he stood in it.
Shadows come up lame :0( figures, we're nearly drowning here in mass and theres water and puddles everywhere but I can't ride him right now. I really like the idea of having someone infront feeding him treats, he's a big piggy so im sure that will be a good tactic to try. Thanks everyone, ill let you know how it goes once we get going again :0)