We would not be without the sea. Without the sea, no clouds, no rain, no rivers, no life. We play at its edges, we put down nets and feed from it, we send cargo across its ruffling surface. Yet it remains the wildest, least-known part of the planet. For too long we have turned our backs to it. This issue looks outward again, with James Hamilton-Paterson, Julia Blackburn, Neal Ascherson, and more.