Most of my cats have had the "water patting" habit. I always thought it was so they could see the water, making it easier for them to know how much to lower their heads so they wouldn't get water up their nose. My remaining elderly cat always wants a *fresh* bowl of water. I think this is because the temperature of it is different from room temp, again making it easier for her to drink without getting water up her nose. But I could be wrong......