Crawfish, Palinurus elephas - or European Spiny Lobster to use its correct official name, is unfortunately a rare animal these days due to over-fishing and collection by divers. They are seasonal and live inshore in the summer, migrating to deeper water for the winter. They have recently started to appear in the North Sea and this specific picture is only the second record for that location.
St. Abbs Marine Reserve, Berwickshire. E. Scotland