Book excerpt: For over two decades Two Oceans has been the pre-eminent book to which scientists, students, divers and beachcombers turn to identify and learn about marine life, from sponges to whales and seaweeds to dune forests. In this exuberantly colourful, fully revised fourth edition, over 2 000 species are now covered, names and other details have been updated to refl ect the latest taxonomy and many new photographs have been added.