I replaced the threaded polystyrene balls (see "Watching the tides") with another foam like substance: popcorn - a biodegradable form of polystyrene I thought.
At low tide (2:22pm) the sea looked very quiet. At about 3pm I marked the edge of the water with two sticks: to hold the thread and mark the water level (image 1).
The tide started to come in again and the waves showed their full power: image 2 and 3. The threaded popcorn looked nothing but fragile - it jammed and was torn apart.
After about forty minutes the water level was high enough to submerge the sticks - a last bit of the floating thread still swimming with the waves: image 4. It will eventually get loose and float away.
I got a big laugh for this from my companion. - Well... this is how my work develops.