SEDNA IV and its crew embark on a three-year expedition to document the incredible beauty and wealth of species on this planet, as well as to bear witness to the state of the biosphere and its relationship with humanity.

San Francisco stretches on a peninsula surrounded by the Bay of San Francisco to the east and the Pacific Ocean to the west; charming and quaint with its multicoloured Victorian-style homes and its many ethnic neighbourhoods, it is wonderful to visit.

The Panama Canal is one of the largest canals in the world and shaves 8,000 miles off what would otherwise be a two-week voyage for the 14,000 vessels that pass through it annually; the most risky manoeuvre is when northbound ships meet southbound.

Having completely transformed itself over the last 20 years, Lisbon has become Europe's most cosmopolitan city; a recent arrival into the European Union, this vibrant metropolis continues to welcome waves of immigrants.

RATED PG. In Botswana's Okavango Delta, Dave and Cody seek to escape the dangerous and deadly hippo-infested marshland using only a dying GPS and waterlogged binoculars.