It is totally normal for a baby to need to eat in the night for at least 1 year. My 11 month old just dropped her nighttime feeding, although she periodically still wakes for it. Just one feeding is AWESOME for 5.5 months!
I have always said that I don't get to stop being a mom or meeting my child's needs just because it's night time. Getting up once in the night is really not bad and he obviously really needs to eat and is hungry since he finishes the whole bottle. You'll hear of other babies his age that sleep straight through the night, but realize this doesn't mean that YOUR SON is ready to do that. There are just as many babies who are over a year (or even 2 or 3 years) who don't sleep through the night. He will do it when he's ready, and most babies stop waking to eat in the night as they start eating more and more table foods.
Also, I would be very careful about giving water. First of all, there is no nutrition in it, and your child needs nutrition at this crucial time of growth. More importantly, however, too much water can cause seizures and even death from hyponatremia. I started giving sips of water in a sippy cup around 6 months, but no more than that.