We started parent-child swim classes when DD was six months, she she loved it! I second some of the advice above, especially the quiet/empty pool if she seems scared. I think my DD was more startled by the echoing noise and people than the water. Some of the activities they led us through included:
- Hold baby on your hip and bob up and down, getting wetter and wetter until you're down to your chins in the water.
- Hold baby facing you, at arm's length, on her belly, with your hands under her chest and her chin resting on the heels of your hands. Pull her around, and practice blowing bubbles and kicking.
- Hold baby on your shoulder in "burping position" with her legs floating out behind her and move around. This is a good one if baby is timid.
- Back floating, with your hand under her neck, supporting her body as much as she needs but helping her experience floating. (My DD wanted to put her legs straight in the air so this never worked for us.) :)
- Getting in and out: Helping baby go through the motions of sitting on the side of the pool, twisting around, putting her hands down, and lowering herself into the water. Then approach the side, put her hands on the side, and practice pulling up and twisting around to sit down.
Mostly, just have fun! Splash, kick, float, and cuddle. Build trust, rather than trying to get her to swim or DO anything in particular. There were babies in the class who were terrified, and the more the parents/teacher tried to distract them with an activity or involve them in the class, the worse it got. Don't worry if she wants to cling to you, just enjoy the water together. They also make water-safe mesh baby slings!