The second edition is extensively revised and updated, the number of pages having increased from 224 in the first edition, to 312 in the second edition. British and Irish shallow seas contain an astonishing 6% of the world's seaweed species, more than 600 different seaweeds, and yet most divers, snorkelers and rockpoolers can put names to only a handful of them. This photographic guide aims to de-mystify seaweed identification for the non-specialist. Over 235 species are described in detail, with colour photographs, information on habitat, distribution and confusion species. Species are divided into three main sections, red, brown and green seaweeds, each with its own identification key and introduction. With over 550 colour photographs and illustrations, Seasearch Guide to Seaweeds of Britain and Ireland is an invaluable aid to any person wishing to identify seaweeds. Seaweeds of Britain and Ireland has been produced as a part of the Seasearch project, which offers training in the identification of marine life and habitats and encourages recording by volunteers.