In its largest expansion since opening for business four decades ago, Funtown Splashtown USA is adding two water slides that will be nearly seven stories tall. The public is demanding water rides with bigger thrills, said Kenneth Cormier, the park's founder and president. So he's replacing the amusement that started it all: the park's little-used miniature golf course. In its place, visitors will find the Tornado, which looks like a giant megaphone, and the Mammoth, a pumped-up version of the park's existing corkscrew slide.