Swim diapers, unlike regular diapers, are only meant to retain solid waste. They do not hold urine because they are unable to distinguish between urine and water, and if they were absorbent, swim diapers would pose a hazard because they would swell and become heavy. For this reason, regardless if you use a washable or single-use swim diaper, you do not want to put your child into a swim diaper until you are ready to get into the pool.
Will a swim diaper contain runny, breastfed poop?
Customers are often skeptical of a swim diaper's ability to contain breastfed poop, however, you can rest-assured that if your little one is wearing a swim diaper that fits properly, it will do it's job. If your baby does poop in the pool, even though it will be contained in the diaper, you will still have to get out and change her swim diaper (a poop in the diaper is still a poop in the pool!). For this reason, it's a good idea to pack a spare swim diaper 'just in case.'
What style should I buy?
Single-use swim diapers pull-on, however, they are made with a tearaway seam at the side of the diaper so you can tear it off. Washable swim diapers are either pull on, or wrap-style. Pull-on swim diapers can be a challenge to get on (especially with a small baby), as you have to shimmy that baby into the swim diaper. Furthermore, if you have to take a poopy swim diaper off, a pull-on swim diaper must be pulled off. Think about that for a minute. Easy-on and easy-off aside, a wrap-style swim diaper also offers a customizable fit.
Sized or one-size?
It was only a matter of time, but since one-size cloth diapers have become popular, manufacturers have introduced one-size swim diapers to the market. Given that 'one size fits all' translates to 'one size fits most', we have elected to eschew this new trend. When the only thing standing between your baby's turd and a pool evacuation is a swim diaper, fit is important. Something that fits well is going to do a better job that something that fits OK.
Velcro or snaps?
A wrap-style swim diaper will be secured with snaps or Velcro. Both offer their own advantages. Velcro is quick and easy, if you have a diaper Houdini, this can be appealing (especially when you're trying to negotiate a public pool changeroom!). Some people prefer snaps because they don't like the feeling of Velcro rubbing against their skin or bathing suit if they are holding their baby on their hip.
Can I use a regular old diaper as a swim diaper?
You can, but we would only recommend it in a pinch. Regular diapers are sized assuming there is an insert in there, so an empty diaper (or diaper cover) will fit differently with nothing in it. Furthermore, regular diapers are laminated, so they will hold fluid in the pool (like a plastic bag, it will catch water, when you pick your baby up out of the water, or move them through the water - a swim diaper will allow water to filter through the fabric). If you do use a regular diaper in a pinch in a public swimming pool, be sure to rinse it properly immediately after you leave the pool - public pools are typically highly chlorinated, and chlorine can ruin your diapers laminate.