This is a watercolor painting of a sea slug. The sea slug is a vibrant red color with a lighter, almost white, underside. It has a long, flowing structure extending upwards, resembling tentacles or gills, which are also red. The body of the sea slug is elongated and somewhat flattened, with a textured surface. There are small, white spots scattered across its back. To the right of the sea slug, there is Japanese calligraphy, likely labeling or describing the creature. The calligraphy is written in black ink on a light background. At the bottom of the image, there is a number '75766' written in black ink. The background is a pale, creamy color, giving the painting a vintage or historical feel. The style of the painting is detailed and scientific, suggesting it may be an illustration from a natural history study.