I teach all my horses to swim. I never heard of a horse that would not swim (until now), it is their natural instict.
Usually we go in the water bareback, as I do not like my saddles to get wet and I think it is better and easier for the horse, especially when it is not used to it.
First introduce your horse to the water from the ground, on a long lead line, maybe even with a horse that is already a good swimmer. (Love to train my horses that way - with experienced horses, makes the job so much easier).
Let it go in deeper, and out again and deeper again and out again, do not rush the horse. Eventually it will swim and see that is not a bad thing.
Swimming with horses is so different for them and you! I love it and do it almost every day in the summer. If you swim in the lake I would not worry about my clothes to much but if you go in the ocean, go with as less tack and clothes as possible as the salt water eats everything after a while.
My little 14.1hh pony swims, so does my 17.1hh warmblood! They love it, but I did have a little paint mare that had really small feet and she had a hard time swimming, she did it but it was a lot more work for her than for my other horses.
We are so lucky to live only a 15 minute ride from the river, so we go at least once or twice a week in the summer. Now, we hardly ever are actually swimming, as it's pretty shallow. But it gets up to about shoulder height on our 14hh ponies. There are places it gets deeper though. My horse personally LOVES water, and her son seems to have inherited her waterhorse trait, at least, at 3 weeks, he loves hoses and any water. Our older Haflinger tolerates it, but doesn't love it. What we ended up doing last summer was just tying her to a brick 5ft out from shore (The water was probably only 8inches or so) and just let her play with it and all while we wandered and floated with my horse.
Both my mom's horses have loved water, as long as they can splash it at their and other horse's riders. :)
We have had several times we found deep spots and actually swam, and, at least for Tiara, it was just like we were walking along, and suddenly she got very smooth and the water flowed over her back, then she found solid ground and starting walking again. She was completely calm about it.
There was one very scary time though. We were very board and hot, so we just decided to follow the creek through the woods. It's pretty small, maybe only 20 or 30 ft across, and this was during a drought. We were walking around a bend where there was a big, rooty tree on one side and a pile of sticks and rocks and debris on the other. The water had never gotten over knee height, so we just walked straight in. They were a bit apprehensive, and rightly so, because it turns out the river just drops off there. We were walking along, and suddenly, the ground seemed to have disappeared. Tiara got scared and actually part-way reared, stretching her back legs out, and they STILL didn't touch bottom! She then turned and plunged, scrambling over the pile of debris. My friend was able to turn Troya around before she fell off the edge. I was able to stay on, thank god, and we were all unhurt. But that just goes to show, be careful around water, especially creeks and rivers. They sometimes just drop off. We know a place around here where there is a small river. In on spot it's maybe 2 feet deep, and lots of families come there to let their kids run around in it. Then, 200 feet upstream, it drops off 150 ft and people practice scuba diving there.
Anyways. When we go, we usually ride down to the river in shorts, bareback. We sometimes wear boots and take them off, or just wear sandles. We take off our helmets, and either go in halters or bridles, depending on the horse. Just make sure to oil the bridle after, if it's leather.
When I was a kid we (my barn friends and I) would take our horses and head straight for the pond during the summer. It was a lot of fun, even though once my horse spooked, went sideways, I went of the side with one foot getting caught in the stirrup and got dragged under water until my foot came out. I don't advise playing in the water with a saddle on, because of that, but that's just my opinion.
How awful for the lady whose horse drowned.
Not all horses will swim.
Make sure that wherever you swim there is not any quicksand around. The river around here has spots that will suck you down, and horses have died.
I had a horse get stuck in some and finally got him free, did that ever freak me out, and I forced him to go forward, always listen your horse !
I just went to Horse Lake, yes it's real lake with that name, took him took the boat launch spot and rode him in. I put a lead rope around his neck to turn & hang on with. Was a really cool feeling! Swimming with my horse - YouTube