Nudibranch are like little flowers. They are often colorful. They actually are mobile. I usually see them alone.
Three in one spot is a treat. There is always room for one more image. The usual image includes the horns and the gills. Everything needs to be sharply focused.
And a nice background is a plus. All sizes, shapes, and color are present on the reef. Each time I see one I take an image. Someone asked me why I take repeat images of the same subject. Good question…next?