This is the Fal River in SW Britain.  It is a ria that is sometimes visited by dolphins and is the site of an eDNA assessment project.

The ground-truthing of dolphin occurrence is usually difficult, particularly at night.

At this site an F-POD is stationed on a mussel farm and provided clear quantitative evidence of dolphin vists, most at night.

But the Fal was the first site where WUTS – weak unknown train sources – were discovered, so this creates a significant data validation task.