Organotin antifouling paints are degraded relatively rapidly in seawater mainly by microorganisms, but they have high affinities to sediment and organisms in the sea. The concentrations of tin in seawater have been observed to decrease in many harbors in the world since the ban to use the paints for small vessels came into force, however, in a few areas frequented by large ships, organotin compounds continued to be input onto the surface of the sediment. Therefore, recently, the number of articles on the investigation of depuration of organotin compounds by organisms have increased. For example, pyroverdins, azotochelin and ornibactin obtained from microorganisms such as Pseudomonas chlororaphis and Burkholderia cepacia, and organisms such as dinoflagellates, diatoms, mussel, green algae and chrysophytes are able to depurate organotin compounds of TBT and TPT in seawater. Furthermore, with the help of these depuration technologies, we hope that the marine environment will improve in the world, at least up to the point in time where environmentally friendly best alternative antifouling paints are used routinely for all vessels.