A single orange ellipse represents a fish swimming repeatedly across an 800-by-600 SVG viewport on a light blue background, looping infinitely with a linear ease and a fixed eye dot that moves in sync. The animation uses d3.v7’s `selection.transition()` and `selection.attr()` to update the horizontal `cx` coordinates over an 8-second duration, resetting to the off-screen start via the `on("end")` callback. The shapes are drawn directly with SVG `ellipse` and `circle` elements, with no external data source.