I agree with PoolDoc, and have had some similar experience with trusses. My college years summer job was raising tents and building temporary dance floors for large outdoor parties. We did alot of highly customized work and regularly built floors over pools. We had trusses built by a local shop who built trusses for warehouses. Ours were painted steel but they were never installed for more than a week at a time. We attached wood blocks to plates at the ends of the trusses to prevent damage to the pool deck and coping. We spanned the pool with 3 or 4 trusses and built a floor on top of them with 2x10s and plywood. These floors could be installed without getting wet.