For the age one and up set, Cara is a strong supporter of life jackets. Not swimming pods, not floaties, not rings, but U.S. Coast Guard approved boating life jackets. Overkill? Maybe. But better safe than sorry in this instance.
Cara's first summer at the pool was when her youngest was 1 and the oldest was 2 1/2. Both boys refused to stay anywhere near the baby pool, nor would they stay in the stroller. Nope, they wanted to be where the action was - in the big pool. As a former competitive swimmer, she resisted the notion that life jackets were the best solution, worrying that they would become a crutch and neither kid would ever want to swim without them. After just two trips to the pool with the boys by herself, she determined that she'd rather have high schoolers in life jackets than toddlers at the bottom of the pool, so she caved. Don't you know those boys are 4 and 5 now and swim (without life jackets) like little fish. Cara would allow them to take turns swimming with their life jackets off, or if she had Dad or other extra hands along, the life jackets could stay at home. But even now, she brings the life jackets along every time her Bunch checks out a new pool. The boys wear the life jackets until everyone is fully slathered in sunblock and set up and Cara has had a chance to scope out the lay of the land (depth of pool, location of stairs/ladders, etc.) and is confident that she can safely supervise all children.
Please note that life jackets DO NOT mean that you can lounge poolside chatting and drinking a margarita while your little swimmers bob about. You still have to stay on constant alert. Cara uses a method called "triangulation" that she learned while life guarding as a teenager. This basically means that you are constantly scanning your eyes across each of your children and any other identified hot spots (such as exits or other hazards). Cara uses this technique not only at the pool, but at the playground, the Children's Museum, and during any other items, as a way of making sure that she is constantly on alert for the whereabouts and safety of her crew.
Some pools, like Linda's, do not allow life jackets, and this presents additional challenges. Linda's methodology was to only allow her kids to go to the baby pool unless another adult was present. This was teh rule from the first day. No other grown up = baby pool for everyone.
For smaller babies, life jackets are no good because they are designed to flip the baby on his back, which he usually does not like. In this case, the floating seats/rings are handy to have. Even as small babies, Cara's kids all preferred the ones with mesh rings rather than blowups, because they wanted to have access to the water so they could splash. Of course, these can be easily tipped by older kids, so when you use them you will want to keep one hand on/near baby and the seat at all times.
Since your older child will likely be the most active and most vocal about wanting to swim, try to work around that child's demands. Frequently, the best plan of attack is to leave the youngest/least mobile child strapped into the stroller until they start complaining. This allows you to get comfortable with the facility and your older child's limitations before you have to manage both kids at once. Conversely, if the baby always complains to get out of the stroller, let them come in the water and you can get them good and tired - frequently they will go back to the stroller with nary a complaint and spend the rest of the outing staring at the pool, glassy-eyed and exhausted.
Another suggestion is to always hit the pool with friends. This is not so you can all commiserate on how much it sucks to go swimming with your Bunch. It is so you can divide and conquer supervision of the children. Place yourselves strategically in areas throughout the pool and supervise each other's children in that area. Naturally, everyone is responsible for their own children, but it is highly unlikely that all children present will start drowning at once and moms seem to have a sixth sense for seeing/helping kids who are struggling in the water. It can't hurt to have an extra set of eyes and Mommy Pool Radar scanning the pool area.
One final note is to forget about counting on lifeguards. They are typically high school or college kids. While some are very responsible and watchful, others are more concerned about working on their tan or flirting with the lifeguard across the pool. Cara knows this because she was one once. The lifeguards are concerned about general safety in the pool area but they are not being as vigilant about your little one's safety as you are. Never count on them to do what is your job. (Note: Linda has saved both her kids from nearly drowning when a inflation device tipped over. The lifeguards didn't even flinch.)
It's not easy to take your Bunch to the pool, but it is possible, and it gets easier every summer as they get older. Now go have fun!