From what I've gathered, it seems if you wear a regular disposable diaper in the pool, it'll soak up all the water and get really really heavy and bulky. It might even "explode", with chemical-loaded stuffing going all over the place. A disposable diaper specifically designed for swimming is better, though it will probably still soak up some water and for this reason you'll need to change the diaper as soon as the child is out of the water. Apparently washables have the opposite problem - they are not meant to absorb, just to contain. So, pee will flow freely into the pool. They do say it's sterile, but still. As soon as baby is out of the water, you'll have to put something more absorbent on them - either a new diaper or an insert into the washable shell. The benefit of the washables is that, assuming there's no poo, you can rinse out the diaper and reuse it all day long. The price of one washable swim diaper is about the same as a pack of disposables, and will fit for at least 1 summer season, possibly two. Depending on how much time your baby will be spending in the water, one may be better for the budget than the other.
What I'm mostly worried about is poo. Kenzo's only 4 months, and will be around 6 months during peak summer time. As a breastmilk only baby, he's pooing out a disturbingly gooey brownie batter type substance, that unfortunately does NOT smell like brownie batter! I can only imagine him splashing about with the other babies in a friend's kiddie pool when he lets one rip. I'm sure we'd never being invited back again >_< Or how about at the public pool, where hundreds of people will be forced to clear the pool while they clean up my son's explosion. How humiliating!! SO, figuring out a good swim diaper is pretty important here!!
Alpha Mom did a great write up on disposable vs. washable swim diapers here. She's quite pro-washables, though I'm just still not sold on them handling Kenzo's poo. If you do go the washable route, it seems velcros or snaps are preferable to pulls on, because it's a lot easier dealing with poo clean up, or if baby has sandy and sunscreeny thighs.
And the kicker that has me doubting whether I'll ever let my little one into any pool, a message from our dear friends at the CDC that swim diapers *may* delay poopy disease-carrying bacteria from entering the water for a couple of minutes. And it seems chlorine can not be counted on to kill everything. They also mention that urine binds with disinfectants to contaminate air quality in indoor pools. F$&%! And to think it was Jaws that made us not want to get back into the water. Now we have a lot more to worry about...
If you're still interested, here are some options and prices I found:
WASHABLE OPTIONS: (in order of my interest, best on top)
* Bummis Swimmis - $14.50, velcro on both sides (pictured below - how cute!)
* FuzziBunz - $20 - regular cloth diaper, just leave out the insert for swim time; snaps on both sides
* Imse Vimse - $30 - snaps on one side
* iPlay - $10 - snaps on one side.
* The Honest Company - $13 - One size fits all, pull-up style - not sounding so great.
* Pampers Splashers - 24ct - $9 ($0.38/diaper)
* Huggies Little Swimmers - 12ct - $13 ($1.08/diaper)