The Chen-4 or Sinking-4 (沉-4, or Chen-4) naval mine is a small Chinese bottom mine with non-contact fuses. It was jointly developed by the 710th Research Institute of Chinese Shipbuilding and the Dongfeng Instrument Factory (东风仪表厂). This mine is the bottom mine counterpart of the Drifting-2 drifting mine, and like the latter, it can be disassembled for easy transportation then reassembled prior to being planted.