While water may be introduced to 6 month olds and older, it is not necessary. Breastmilk or formula will be enough to meet their hydration needs. As long as your baby is having regular wet diapers, there's no need to worry. However, you may want to offer sips of water (no more than 2-3 ounces/day so it doesn't displace milk) to help them practice cup drinking and to get used to the flavor of water. Drinking from a cup is a lifelong skill, and by introducing early, it will give them plenty of time to explore and practice. Yes, it’s going to be messy but will be well worth it when it comes time to transition your baby from the breast or bottle. By then your baby will have the skills to drink independently and will easily be able to make the shift. Keep in mind the goal at this stage is not to get them to drink a large amount of water. It is practice practice!