The Opening refers to the mouth of an undersea cave or crevasse. The perspective is that of a diver, who's entered the cave and is looking back, through the opening, to the sunlit surface. This motif was used in the Squid series, with relief printing of squid in chartreuse over black. The background grabbed enough attention to warrant it's own series, which evolved to include impressions of kelp and other algae rising to the surface.