An interesting question on which different people have different views.
I think that there is no harm is sipping water during the meal. The key thing from health point of view is proper hydration during waking hours, especially mornings. A simple formula to calculate the amount of water is: divide your weight in pounds by two, whatever the product is the amount of water in ounce you need to drink. Suppose your weight is 120 pounds. Divide 120 by 2 and you get 60, so you need 60 ounces of water per day to remain properly hydrated. This is about 1.7 litres of water.
In India, people follow a thumb rule of 8 to 10 mid size tumblerful of water per day. And water is an essential accompaniment with any meal.