For our swimming class, we have to use a double nappy system, with a 'normal' nappy on first, followed by a neoprene Happy Nappy. Our class fees included five Pampers disposable swimming nappies, but now we've used most of these I want to start using reusable swimming nappies for the bottom layer. Any recommendations for what to use as our 'normal' (but reusable) nappy? The class insists that we use a Happy Nappy over the top, so the reusable nappy must be slim enough to fit beneath it.