Paddling in the little river, I noticed a strange stone shining in the mud. I picked it up. No stone, but a shell. A beautiful, blue bivalve shell with silver and gold contours. As I tried to work out what it could be, a bowl of moules marinière popped into my mind. Had someone enjoyed an unseasonal seafood barbecue upstream and tossed this shell away? Excitement grew as I realised that I was holding some kind of mussel, and it was still alive.