We always used the Swim Nappies which you can get from K-Mart - they come in a small plastic pocket thingy, they aren't disposables so are 'financially friendly'. When we went on holidays we had 2 lots so if we swam in the morning and they weren't dry by the afternoon Miss M could still have a dry one put on. (Nothing worse then putting on wet swimmers!). I think there was a thread not long ago asking about swim nappies too.