What lies beneath the world's oceans? From the phenomenal infrastructure of telecoms cables to shipwrecked galleons and treasure and the sea creatures of the literary imagination - we explore the mysteries of the deep. Adam Rutherford chairs Radio 4's discussion programme which starts the week. His guests are:

The writer Julian Sancton is the author of Neptune's Fortune which tells the story of Roger Dooley, a diver who went in search of a lost ship. An accidental discovery in the archives led the unlikely treasure hunter to search for the shipwreck of an eighteenth century galleon, the San José. Laden with riches on its way to the New World, it was sunk in a fierce battle and its location was forgotten for centuries. The pursuit is a tale of maritime archaeology, rival treasure hunters, legal and political obstacles and the challenge of narrowing the search to a small area of the sea bed.

We think of the internet as wireless, but it is connected by nearly 900,000 miles of fiber-optic cables at the bottom of the ocean, stitching whole continents together. In The Web Beneath the Waves, the journalist Samanth Subramanian explains the secretive cable-laying operations behind the world of undersea infrastructure. He discovers the environmental risks to them, corporate interests over them and the acts of “grey zone warfare” when ghost ships cut the cables of other countries.

Joan Passey is a senior lecturer in English at Bristol University and a BBC Arts and Humanities Research Council New Generation Thinker. She is the co-founder of the Haunted Shores Network and a leading researcher in literary study of coasts and seascapes, combining an understanding of folklore, myth and technology.