You cannot use regular diapers in a pool. They'll dissolve and put all of the absorption junk in the water. Ick.
I have used little swimmers, but I prefer cloth diapers for the pool. The previous poster seems confused - I am not recommending regular cloth diapers. I am recommending cloth swim diapers, which are specifically designed for swimming. I would think a regular cloth diaper would do nothing in a pool. There are lots of brands of cloth swim diapers, and in my opinion, they work better than Little Swimmers.
No swim diapers hold-in urine (and they're not designed to), whether cloth or disposable. But disposable swim diapers swell up the moment they hit the water, so I don't know how much good they really do. The cloth diapers don't swell, hold in the solids, and cost a lot less in the long run. You can find Bummis Brand cloth swim diapers on amazon.com, and Babies R Us sells some that look sort of like rubber pants (they are in the beach section, not in the diaper section). My favorites are from onestepahead.com, just do a search for swim diapers. There are two kinds - one with adjustable sizes, and one that fits tighter but you have to buy larger sizes as your baby grows. They do not expand when wet, which is really nice. You'll spend about $10-$15 on a swim diaper that will fit for quite some time, so by buying cloth, you'll save money, too. Good luck.