I was amazed when I noticed this six armed vermilion star (Mediaster aequalis) resting on the rocks below. Up until this point I’ve only seen this sea star species with five arms.
Sunlight contains all the visible light we see (red, orange, yellow, green, blue, violet) and appears white, but when sunlight penetrates into the ocean red light is the first to be absorbed with increased depth. The result is that what appears red to me (when illuminated by my dive light), appears blackish to other underwater creatures in natural light at that depth, and so it’s interesting that this bright sea star tends to disappear into the reef. The vermilion star can grow to 8 inches (20 cm) across, and has a range from northern Alaska to northern Mexico.