Why do divers see brown algae black?

As you know, light is the rays of the visible and invisible spectrum of lines. At a depth of fifty meters, the blue and green tones are made to resemble the colors of the ocean. To a depth of fifty meters, ultraviolet rays still penetrate the water column. At a depth of twenty meters, it is already difficult to distinguish the bright color of the animals. When descending to a depth of ten meters, only a greenish-blue color is visible. Red tones at a depth of twenty meters will appear brown, and at a depth of forty meters, green. The seawater layer absorbs light and distorts it, only green and blue rays are transmitted.