Victor Vescovo: 'The opportunity to do great science'

US adventurer Victor Vescovo has become the first person to visit the deepest points in every ocean.

His fifth and last descent in a submersible was made to the bottom of the Molloy Trench in the Arctic, some 5.5km (3.4 miles) below the sea surface.

This followed dives during the past 10 months to the floor of the Pacific, Indian, Southern and Atlantic oceans. The millionaire financier's team also visited the wreck of the Titanic.

He spoke to our science correspondent Jonathan Amos about the elation he felt when his sub surfaced in the Arctic at the end of the last dive.