As much as you'd like to, you can't really plan a water birth. Also, it's not that clear-cut as what's a water birth and what isn't, IYSWIM.
With my first, I spent around 15 hours in the water pool but he ended up being born on dry land when it all went pear-shaped.
With my second, she was born in the water after a labour of less than an hour. So even though my 1st labour wasn't technically a water birth and my second was, I had much more of a water birth "experience" with my first, considering the amount of time I spent in the pool.
My tips would be - don't get too hung up on it as an idea, unless you plan on a home birth and hiring your own pool. You don't know if the pool will be available at the hospital, and you don't want it to be a disappointment on the day if it's not free.
Also, as much as you might like the pool, your baby might have other ideas. DC1 didn't want to be born in that pool despite all the dimmed lights and water and hypnobirthing shite I thought would work.
Then with DC2 my "plan" was to go to the hospital and just see what happened. She was born in the pool with no pain relief - just as I'd wanted for DC1.
You can have all the plans you like, but if your baby (and pool availability on the day) will mean you'll just have to go with the flow.