Well...honestly, typing this makes me laugh. We started swimming lessons for my Daughter at 6 months, she'd always loved the bath and had been 'swimming' in the bath for a while. We got there, got in the pool and its safe to say that my Daughter turned into a screaming, hysterical wreck and to this day (she is nearly one) she cries whenever I put her swimming costume on her, lol I know I shouldn't laugh but honestly, it was like a comedy act. She hated it but I honestly believe she hated the atmosphere (lots of screaming and loud babies) rather than the actual swimming because at home, in the bath, she even puts her head under the water with her eyes open to get toys from the bottom of the bath.
I definitely know more babies that have loved it rather than hated it but just be prepared that it usually takes babies out of their comfort zones, so she might not take to it instantly.
Good luck with your little water baby :)