Few places are as familiar as the shore – and few as full of mystery and surprise. In the sea is not made of water Adam Nicolson explores the multiple, interleaved layers of that world and the long human relationship with the shore. How do sandhoppers inherit an inbuilt compass from their parents? What is it that prawns know? How do crabs understand the tides? How can the death of one winkle guarantee the lives of its companions? Connections animate the book. The physics of the seas, the biology of anemone and limpet, the long history of the earth itself, the governing myths and stories of those who have lived and survived here: all interconnect in the zone where philosopher, scientist and poet can meet and puzzle over the nature of what exists. The intertidal has been the scene for all kinds of scientific discovery – from the workings of evolution to the intricacies of biological networks. But its story is as much human as natural history: how far should our own lives be understood as an aspect of ecology? Do our buried beliefs about the tidal sea reflect a fundamental understanding of our relationship to nature? And is it the shifting condition of that tidal world, its pervasive uncertainty, its fierce interfolding of opportunity and threat, that makes it one of the most emblematic and revelatory habitats on earth? the sea is not made of water is an invitation to the shoreline. Anyone who chooses can look beyond their own reflection and find the marvellous there, waiting an inch beneath their nose.