A photograph of debris can be striking while covering only a few square metres. Before using it to describe a shoreline, ask what lies outside the frame. NOAA’s marine-debris overview introduces the wider issue and links to monitoring resources; a personal photograph serves a much narrower purpose.
State what the image records
Note the location, date, and approximate area shown. If the photograph was chosen because it contained an unusual concentration of items, say so. A deliberately selected patch is not a random sample of the whole coast.
Describe visible items without assigning origins you cannot verify. A label or familiar shape may suggest possibilities, but it does not establish the route an object took to reach the site.
Pair the image with a method
If you want to compare visits, decide how the area will be selected and photographed each time. Use an established monitoring protocol when contributing data to a project. Otherwise, label the images as personal observations rather than a formal survey.
The boundary makes the photograph more useful, not less compelling. Readers can understand precisely what it shows and avoid drawing a coastline-wide conclusion from one chosen view. Strong visual evidence still needs a clear statement of its scope.