The WaTiki Indoor Water Park Resort in Rapid City, S.D., will soon expand in order to accommodate a new hotel and conference center, its owner, ISIS Hospitality, recently announced.The resort, which is home to the Dakotas' largest indoor water park, will commence its expansion in spring 2010. Upon completion, WaTiki—which currently has two hotels, including a 141-room Fairfield Inn & Suites and a 116-room LaQuinta Inn & Suites—will have a 150-room SpringHill Suites by Marriott hotel with a new, state-of-the-art 12,000-square-foot conference center.Additionally, ISIS plans to double the size of the actual water park, installing a $1 million artificial wave surfer, adding several "extreme" slides and building a 10,000-square-foot outdoor resort pool with swim-up bar.A completion date for the expansion was not announced.