First thing I'd say is not to think of a "water birth" as a separate thing. It's not a case of one or the other, water birth or "land" birth.
For example, most people I know were in the water for part of their labour but none actually gave birth in the pool.
I did about eight hours in the pool. It was very pleasant and helped with the pain until things got more complex. As it was, I had to be transferred to the consultant-led part of the hospital, so had to get out of the pool, but to be fair it had long ceased to be even touching the sides of the pain. In the same way that a hot bath wouldn't help a broken leg, but might soothe a headache.
If you have an "easy" birth then I'm sure the water will be enough to help throughout. It's certainly good for relaxation - we had low lights, music, hypnobirthing mantras, all that jazz. And for several hours that was all well and good.
But it might be better to think of the pool as just one tool in your kit rather than the whole shebang. It could be a useful stepping stone.
I haven't decided yet if I'm hoping to get in the pool this time round. I'm certainly not doing hypnobirthing...