just a shallow one, not until the chin level becoz they may be frightened...somewhere at the waist level will be fine. (most baby pool is somewhere there)
make sure she dont get scared during the session, put her in water slowly. If she is afraid let her play with water a bit first (splash on the toes, hands etc) before going into the pool. Once she starts to be curious and is not afraid then you can put her into a float and let her swim around...just take it one step at a time. Also remember to keep her warm when outta water with towels. Rem to apply sunblock (spf 50 esp for babies, you can get them in all major baby stores) She is not walking on her own yet rite? If not, its better to go along with older kids or more pple around so that its more like a family outing/gathering and they can also help to look after yr baby girl as well as play with her.
have fun swimming!