Divers exploring the rocky reefs around Sark this month came across a very rare sea slug. The animal, just two inches long, was found at L’Etac, the islet off the south coast of Little Sark best known for its puffins. Sea slugs, known more correctly as nudibranchs, are often very colourful, unlike their land counterparts, making them popular with divers particularly underwater photographers. Most only have scientific names. This one,…