Portrait of AN Demidov. 1831-1852 Karl Pavlovich Bryullov (1799-1852)

The picture has something of this: people, woman, man, wear, cavalry, recreation, mammal, two, fish, seated, veil, underwater, exploration, side view.
Perhaps it’s a painting of a man riding on the back of a white horse in a wooded area with other men on either side of him and a dog.