This is the Study for 'Bathers at Asnières' by Georges Seurat. Painted in the late 19th century, this oil sketch on wood is closely connected with the final painting of the same name. Unlike other sketches that focus on atmospheric effects or landscape, Seurat's attention here is almost exclusively on the men and boys themselves. If you look closely, you'll see that only two figures from this panel are retained in the final painting: the clothed man lying down in the lower left corner and the young man with the bare torso at the river's edge.
Notice how the five figures in this sketch fill the picture space with a minimal indication of the surrounding landscape. The two larger figures on the right are drawn to a different scale than those on the left, which gives it the feeling of a page from a sketchbook where Seurat is trying out ideas for poses and positions rather than working out the overall composition.
Study for 'Bathers at Asnières' hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.