DD wears her swim nappy and then a swim t-shirt (like a rashie) and a pair of swim bottoms. The swim bottoms don't replace the swim nappy but have been good for holding the swim nappy in place as DD is below the recommended weight for them - they fit her and do contain the poo etc but the swim bottom holds it in place better if that makes sense.

I like the shirt thing on her as it helps me to feel more confident holding her in the water... her bare skin is quite slippery