1) It is possible to prove the fact of crime through the identification of DNA from bloodstains, micro-traces, and body fluids remaining on the tools of the crime even after much time has passed. However, criminals use environmental factors (water, mountain, and the woods) to dispose of evidence, and these environments make it difficult to identify DNA due to various pollutants and damage to DNA. For evidence collected from these deteriorated environments, it is difficult to find traces of crimes due to physicochemical and biological contamination. Thus, it is necessary to conduct a study of the method of collecting DNA effectively. This study would present the possibility of the visualization of latent DNA existing in the evidence at the site (in underwater evidence), using DNA fluorescent dye reagent. Treating it with Diamond™ Nucleic Acid Dye, reported to be the most excellent in visualizing latent DNA, this study investigated saliva and fingerprints remaining on the surface of the materials of general household items. As a result of the research, it was possible to explore saliva and fingerprints on the non-porous surface (Glass, PVC, stainless steel, artificial leather, and black plastic bag) of the materials, and also in the evidence flooded in the sea, it was possible to identify saliva and fingerprints for 3 days when treated with the reagent. Also, there was no impact on STR analysis, a method of identification utilizing DNA. Since it is also possible to detect contact traces and identify DNA for evidence immersed in seawater, crime scene investigators should collect evidence more actively.