Any damage the enemy reflection takes the actual person receives. Right?
No. This technique is merely a genjutsu, or illusion technique, so while the victim feels the pain, it is not real and their body remains intact outside of the illusion.
Q: What happens if ripples are created in the water and the reflection is distorted? Does that weaken the illusion? Does it make you visible for attack?
No, it doesn't affect the illusion. The reflections will just appear rippled as usual. However, the user will have to be careful to 'attack' the reflection when it is moving.
Q: What happens to you during this technique? Do you become invisible to the human eye but you remain in the same spot and only your reflection can be seen?
Since this is a genjutsu, you don't really disappear; you remain in the same spot, and the victim trapped in the jutsu sees you 'vanish'.
Q: Can the person try to attack the reflection using their own reflection against yours?
No, their reflection is pretty much useless.
Q: Would this Technique work on mirrors?
No, it only works on water, as it is a water-release technique.
Thanks for pointing out that specular reflection thing, by the way. I'll add that in. :3