Why does your dog stare into your swimming pool?

Dogs are basically wolves. There is nothing in their genetic makeup that has conditioned them to certain things like clear glistening water, moving without running (head out the car window) and so forth.

Not sure about the above, but so long as your dog is either safely fenced off from going in the pool or wearing a dog life jacket for safety, there is no harm in staring into the pool. If a dog jumps into a pool with no dog life vest on, they can easily tire swimming and usually in a bid to get out. Always ensure your dog does not have free access to a swimming pool that has no shallow end with exit steps or make sure you always have your dog wearing a doggie life jacket when he's around the pool with access, as they prevent drowning.