Wonderful! I love spa days. My daughter and try to do it regularly. Things we have learned:
Take some magazines or a book. You might get fed up swimming, and want to stretch out beside the pool.
Don't worry about the wobbly bits, but if you are selfconscious, take a sarong.
Take a spare swimsuit too, sitting around in a damp swimsuit can get uncomfortable. And if you are having a pedicure, take some flipflops so your nail varnish doesn't smudge.
And try and get a lift there and back. After all those treatments you might feel too relaxed to drive safely.