Salt water covers seventy per cent of the earth's surface: a gigantic challenge to our curiosity and scientific skill.

Tides once a day; tides twice a day; tides two feet high: tides fifty feet high. Every tide is different and our best 'predictions' are still basically guess work.
Peter Stone introduces the fourth of a series of seven programmes.
With Dr. J.R. Rossiter, Tidal Institute and Observatory, University of Liverpool.