The casitas quiet pool is near casita 4. The ranchos quiet pool is near 7B. The cabanas quiet pool is near 9A. Since you booked a waterview room, you can request a view of a quiet pool (other water views are the lake or the fountains).
I haven't used the spa, but Kathy (KatMark) gets a massage every trip.
The casitas quiet pool is next to casita 4 - this is a non-preferred building. Casita 3 (preferred) is also close to the quiet pool. Casita 4 is closest to the bus stop, gym and pool, but since it is a standard building, you can request it, but you might end up in another section entirely.
Your choices (as I see it):
Stick with preferred but request casita 3, ground floor. You can ask at check-in if you can be in casita 4, but I don't think they will refund the room difference. Keeping the preferred room guarantees you will be in casita 1, 2 or 3, at least at the time of your initial room assignment. Even if you are placed in casita 1, you'll be less than five minutes to the pool.
Or, book a standard room and request casita 4. But you could end up in ranchos or cabanas. They each have quiet pools, but the casita quiet pool is the lap pool.
Here is a map of CSR that might help: