The sea grape — violet in French (violet or figue de mer), uova di mare or limone di mare in Italian, biju along the Catalan coast — is a wild Mediterranean sea squirt, a leathery, fist-sized tunicate that clings to rock and harbour stone below the tide. Split open, its rough brown-violet rind gives up a startling fold of soft, bright yellow-orange flesh that is scooped out and eaten raw, on the shell, with nothing but its own liquor and perhaps a squeeze of lemon. The taste is one of the most divisive in the sea: an intense, almost shocking blast of iodine and bitter brine that its devotees on the shores of Provence, Sète, Sardinia and the Catalan coast prize above almost any other shellfish, and that everyone else meets with suspicion.