full formula milk need to feed plain water?

I went for a pregnancy talk and they mentioned no water is to be given to baby below 5/6months. they have to be constantly fed with milk. If I did not remember wrongly, the pediatrician mentioned that water is empty calories to the baby and there is no form of nutrition. They will need to spend the same amount of energy to digest the water and digest the milk. Hence, it is recommended to start giving them water only when you start to feed them solid foods.