A submersible robot for operating a tool relative to a surface of an underwater structure has a tool holder movably mounted on a support assembly provided with a driving arrangement for movably holding the tool in operative position relative to the surface. The polymer film may have an edge into which light is emitted from an adjacent array of light-emitting diodes. Thus, this wavelength selective switch can easily fine-tune the incident position of light with respect to each reflecting surface of a MEMS mirror by rotating the holding member.