LINGAYEN, PANGASINAN, Philippines — One day last month, groups of multimedia arts students from the Pangasinan Polytechnic College (PPC) combed through the Agno River at Barangay Pangasinan in this capital town to pick up “trash.” But this wasn’t a cleanup drive—it was an art mission. From the riverbed, they unearthed a curious assortment of objects: