Build your house in a wetland, and you've got a hobby for the rest of your life,' warns Ed Perry. 'You will be fighting that water forever.' A student of flooded basements and cracked foundations, Perry knows what he's talking about. While investigating illegally filled wetlands in Pennsylvania for the U.S. Fish and Wildlife Service (FWS), the biologist has visited plenty of houses built where water naturally flows and has commiserated with sorrowful owners of sodden split-levels. The lesson, says Perry, is that home builders who tamper with even small wetlands can have big problems.