You can lead a horse to water, but then they may surprise you...
Great film of a horse's reaction to his owner asking him to enter water. Most horses do love paddling and rolling in water – if they have seen it before and are not worried about it. It's an effective way for them to cool down, avoid flies and maintain a healthy coat. Dr. Sue McDonnell at Pennsylvania University reports her herd of feral ponies swim every day in their ponds, and regularly break the ice in winter so they can take their daily dip.
Many of our domestic horses don't have any access to water (apart from boggy fields) and can be anxious about walking into streams, the sea or even puddles. However, once they have realised it isn't going to grab their feet they are often keen to go paddling, splash themselves like this or roll. I do wonder if this is the first time this horse has seen water and he's learning here how much fun it can be.
I love that the owner has led him to the water rather than force him in whilst riding. Horses will often walk calmly with a handler they trust, but may be far more worried by something scary if they are ridden. Having someone on the ground can really boost a horse's confidence. Sadly many riders think it is 'giving in to the horse' if they get off, when in fact it can be a huge help and usually means the horse becomes accustomed to the scary stimulus much faster and is less likely have a problem with it again in future.