NOT ALL HORSES CAN SWIM!
The brother of a very dear friend of ours drowned with his horse is farm pond in Springer, OK about 15 years ago. He was 'cowboying' full time on the ranch and chased a coyote out into a pond where he took refuge. He did not have a gun so was going to rope the coyote like he had done before. Both went down in 12 feet of water right in front of the ranch owner who said he never felt so helpless in his life.
When we first heard about it, we thought maybe they had a tie-down on the horse, but that was not the case. The horse just did not swim.
We swam Arabians in the Lasma Arabian Ranch pool back in the 70s when we trained Arabians. Gene LaCroix almost lost a National Champion mare, *Gdania, in their pool. She could not swim. If a dozen people had not been around to pull her up and out of the pool, she would have drowned.
Another horse and rider drowned in the Red River a few years ago. The guy was crossing the river to bring back a cow that had crossed and both he and his horse drowned.
So, while MOST horses can swim, they all can't I swam my horses a lot as a kid, but I would not do it now. So be careful.
Always remember that no horse can swim with any kind of a tie-down on.