Wow, that horse is high maintenance. He was like "yes! A pool!" and hoped right in. That is actually really funny, it that was me I would be like, "What the heck are you doing!" If he got in there ok I'm sure he got out ok. I would just be worried about him drinking any of the chemicals.
How did he find his way into the pool in the first place though? Did he escape and fall in accidentally? Why is there no fence around the pool? (I know there is a law/by-law here that requires a 5+ foot fence around pools)
His expression is so happy, and he so calmly went to the steps and seemed to know how to get out. And was very careful and not panicked.. I've got to think mister horse is a little fish when no one is looking lol