I found a book called Manual on the Use of Timber in Coastal and River Engineering by Matt Grossman and Jonathan Simm, inside this excerpt.
… In coastal situations timber is used among other things for breastworks, groynes, piers, steps, ramps, boardwalks and as stepped reinforcement or fencing protection to dunes. In river situations timber is used for bank retention/reinforcement, ramps, steps, boardwalks and fishing platforms.
Weathered timber is an important component of beaches, harbours and rivers where it often reinforces the traditional landscape character. The painter John Constable wrote of his native River Stour: “the sound of water escaping from mill dams,… willows, old rotten banks, slimy posts and brickwork. I love such things… They made me a painter and I am grateful”. Similarly, timber groynes, sculpted by the sea and part buried in sand are a classic element of many beach scenes…
This photo was taken on Worthing pier and the above passage captures it perfectly.