Oyster's graveyard?

By popular request today we spent the day at the coast - I wasn't sure if it was for the photography, or for the ice-creams on the way home.

The tide didn't go out quite far enough for us to get to the furthest oyster beds, but we did explore the others. At the far end of these oyster beds, there is this rather odd arrangement of posts and tyres, which looks almost like a graveyard.