Myriad life forms that have rarely been seen are on offer in a special daylong broadcast following three submersibles as they dive to the depths of the ocean. Peter Snow introduces the day's events, helped by cameraman Mike de Gruy, as a 2,000m dive begins beneath their base on a research ship in Monterey Bay, California. Kate Humble, meanwhile, jumps in at the deep end of the Caribbean and Alastair Fothergill plummets towards the mid-Atlantic ridge.
Continues at 4.30pm.
BBCi: continued coverage and other options are available to digital viewers and through BBCi at [web address removed]
Questions: contact details at 7pm
Beauty and the beasts: page 32