From the microscopic 60-metre long Pacific kelp, and from the simple filamentous strings of cells to those species made up from complex issues, seaweeds are very diverse. They are found all over the world from the inter-tidal beaches to the deep ocean, from the poles to the equator. David Thomas brings the life of seaweeds to the amateur, exploring what they are, where they are found, and how they manage to survive such hostile conditions as fluctuating temperatures, salinity and dessication. He looks at how they employ anti-grazing strategies, from tough leather fronds to cells full of sulphuric acid as a deterrent. In places such as the Meditarranean and off the Californian coast Caulerpa taxifolia is an "alien" species, and Thomas looks at this and the effects of other introduced species on the local environment, both biologically and economically. Finally, he explores the multitude of uses for seaweed, together with what you can do whilst combing beaches and rocky shores.