This one came from a passing comment I heard Pat Parelli make, something like, "People ask me how to improve their trail horses. I tell them, squeeze them through every puddle you come to. When they are good at that, they are better at everything else."
I ride out quite a bit, and there are puddles. When I first started this with Jin, she had a lot of problems with it. "Oh my god the horse swallowing puddle! Nooooo I can't step in that!" But every time we were out and there was a puddle, I'd make her step in it. It didn't start out pretty, that's for sure, but sometimes now we have the finesse to specify which foot should step in the puddle first.
Now I tend to do it with all horses all the time. If I've got two horses leading out to their field and there are lots of puddles in the road, I might ask first the horse on this side to step in that puddle, and then the horse on that side to step in the next one. In that situation I'm not insisting, just asking, just suggesting, just taking in information. If I only have one horse, and it is a horse I am riding, then I'm likely to work on it a bit if we need to; "Oh let's try that again how about it?"
What this does is so much I won't be able to explain it all but horsemen will see it. It is an ask, a willingness, a trust, a leadership. It is controlling each foot. It involves whoa and go in balance. It can involve some play, some curiosity.
Last night it was pouring rain as we left the arena and water was flowing through the parking lot. We rode down in the dark. I haven't ridden Zip that much but he's squeezed a few puddles. Last night he walked through flowing water. He was a little unsure but I was like, "We are going to the barn as fast as we dare." "Oh yeah, the barn," he said, and went.
I will add here what a freaking brilliant horse he is. Beautiful for one. Willing. Just opinionated enough. His only "trouble" is he isn't all that athletic.