Photocatalytic　degradation　is　a　leading　technology　for　complete　mineralization　of　organic　dyes　in　the　ocean.　In　this　work,　a　new　viologen-bearing　silver-thiocyanate-based　photocatalyst,　i.e.,　{(i-PrV)[Ag2(SCN)4]}n　(i-PrV2+　=　isopropyl　viologen)　has　been　synthesized　and　structurally　determined,　with　results　showing　that　it　can　exhibit　excellent　degradation　performance　on　rhodamine　B　(RhB)　in　artificial　seawater.　The　planar　i-PrV2+　dications　are　confined　in　the　free　voids　of　the　[Ag2(SCN)4]n2n−　layer　with　a　two-dimensional　(6,3)　mesh,　and　strong　C-H···S　hydrogen　bonds　contribute　to　its　structural　stabilization.　This　photocatalyst　was　further　characterized　by　powder　X-ray　diffraction　(PXRD),　UV-Vis,　fluorescence,　and　photo/electrical　responsive　measurements,　pointing　to　its　application　in　visible-light-driven　catalysis.　Interestingly,　using　this　photocatalyst,　good　photocatalytic　degradation　performance　on　rhodamine　B　in　artificial　seawater　could　be　observed.　The　dye　pollutant　could　be　degraded　with　a　high　degradation　ratio　of　87.82%　in　220　min.　This　work　provides　a　promising　catalyst　for　organic　dye-type　ocean　pollutant　treatments.　©　2024　by　the　authors.