It amazes me how little water people consume these days. About 41.6% of teens are suffering from light dehydration. When I'm out with my friends, they eat as much as a 5-year-old. But, they fill themselves up with sugar-loaded sodas and 600 calorie Starbucks beverages. Strange enough, they tell me that they're on diet. "Drinking" calorie is the worst. It's so much better to eat 600 calories (hey ! You can eat 1/2 roasted chicken with several side dishes and still some space for Frozen Yogurt with that amount of calorie). So if you're thinking on skipping the meal, don't. Plus, sugary drinks do not (read : do not) can't replace water. they may be liquid, but they're more like you eating multiple spoons of sugar (yuck right..)
If you feel that you're skinny enough, it doesn't mean that you should stop drinking water. A human body is 55% - 78% made of water (if you haven't notice, blood is watery and blood is everywhere around your body). That percentage doesn't stay that way if you don't keep drinking. 8 glasses a day should do you good. If you're afraid of going back and forth to the bathroom too much, then drink at night when you reach home. I have one giant jug for me to finish every night.
What's my message here? DRINK MORE WATER ! it's cheap, free of calories and it does wonders for you :)