There’s probably a more technically correct term for it, but I call the stuff that forms a line at the high tide mark “scum” and the line of scum a “scum line”. Simple.
Scum lines can be pretty when they’re made up of thousands of golden melaleuca leaves, rather like an Andy Goldsworthy sculpture. Most of the time though it’s just crap.
Today there was a quite remarkable collection of things that, normally, would get a picture of their own. In one short transect there was a mini footie (with, bafflingly, this printed on its side: “For school use only”), an almost new soccer ball from Adamstown Rosebuds, a crusty blob of industrial foam that looked like the world’s biggest gold nugget or a school project attempt to create a human brain, an orange handball, a magenta tennis ball, a green ball (like those you get in kids’ ball pits at funfairs), a handlebar grip from a scooter, several Ironlak brand aerosol cans, an apple, a Lego block, a bike helmet and a deflated red ballon with the word “Sale” on the side. Can you spot them?